XIV. HEMATOLOGY — ANEMIAS General anemia Q106 — Anemic coma Q112 — Normocytic normochromic anemia Q180 — Anemic syndrome differential Microcytic anemia Q120 — Hypochromic microcytic anemia Q81 — Hemoglobinopathies: thalassemia/sickle cell Macrocytic anemia Q111 — Macrocytic anemia Aplastic anemia Q94 — Aplastic anemia Hemolysis Q50 — Hemolytic crisis Q174 — Hemolysis syndrome Basic to advance answer in detail each question

Reading File

This is a full hematology study module. I can cover every question from basic concepts through advanced differential diagnosis, investigations, interpretation, and management.

Topic map

General anemia
- Q106: Anemic coma: definition, pathophysiology, emergency assessment, causes, acute management.
- Q112: Normocytic normochromic anemia: classification by reticulocyte response, diagnostic algorithm, common causes.
- Q180: Anemic syndrome differential: symptom-based approach, laboratory differentiation, major etiologic groups.
Microcytic anemia
- Q120: Hypochromic microcytic anemia: iron deficiency, anemia of inflammation, thalassemia, sideroblastic anemia, lead toxicity, iron studies.
- Q81: Hemoglobinopathies: thalassemia and sickle-cell disease, inheritance, clinical features, diagnosis, complications, management.
Macrocytic anemia
- Q111: Macrocytic anemia: megaloblastic versus non-megaloblastic causes, B12 and folate deficiency, blood-film findings, workup and treatment.
Bone-marrow failure
- Q94: Aplastic anemia: causes, pancytopenia pattern, marrow findings, severity, supportive care, immunosuppression and transplantation.
Hemolysis
- Q50: Hemolytic crisis: acute presentation, intravascular versus extravascular hemolysis, emergency investigations and treatment.
- Q174: Hemolysis syndrome: laboratory pattern, inherited and acquired causes, direct antiglobulin test-based evaluation.

High-level diagnostic framework

For nearly every anemia question, start with:

Confirm anemia using hemoglobin and hematocrit, interpreted for age, sex, pregnancy status, altitude, and clinical context.
Classify by MCV:
- Microcytic: <80 fL
- Normocytic: 80-100 fL
- Macrocytic: >100 fL
Check reticulocyte count/index:
- Low or inappropriately normal: impaired production
- High: blood loss or hemolysis
Examine the peripheral blood film and targeted laboratory tests:
- Ferritin, transferrin saturation, CRP
- Vitamin B12, folate, methylmalonic acid where needed
- Creatinine, liver tests, thyroid testing
- LDH, bilirubin, haptoglobin, direct antiglobulin test
- Hemoglobin electrophoresis
- Bone marrow examination when marrow failure, infiltration, myelodysplasia, or unexplained cytopenias are suspected

Which section should I expand first in a detailed exam-note format?

General anemia: Q106, Q112, Q180
Microcytic anemia: Q120, Q81
Macrocytic anemia: Q111
Aplastic anemia: Q94
Hemolysis: Q50, Q174

Start with detailed answers for Q106, Q112, and Q180

Reading File

Finding Sources

Searching PubMed

"Anemia"[MeSH Terms] AND "Diagnosis, Differential"[MeSH Terms]

Searching PubMed

"Anemia"[MeSH Terms] AND "Blood Transfusion"[MeSH Terms]

Searching the Web

NICE blood transfusion red blood cell threshold guideline adults 70 g/L 2025

Finding Sources

Reading File

Q106. Anemic coma

Definition

Anemic coma is a state of unconsciousness or profound depressed consciousness occurring in association with severe anemia and critical reduction in tissue oxygen delivery. It is an emergency.

Strictly, anemia alone rarely causes coma unless it is very severe, develops rapidly, or occurs with another insult such as hemorrhagic shock, hypoxemia, sepsis, cardiac failure, hypoglycemia, malaria, poisoning, or intracranial disease. Therefore, never attribute coma to a low hemoglobin value without actively seeking other causes.

Pathophysiology

Arterial oxygen content is determined mainly by hemoglobin:

[ CaO_2 = (1.34 \times Hb \times SaO_2) + (0.003 \times PaO_2) ]

Oxygen delivery to tissues is:

[ DO_2 = Cardiac\ output \times CaO_2 ]

With severe anemia:

Hemoglobin falls, so blood carries much less oxygen.
Compensatory tachycardia and increased cardiac output initially maintain delivery.
Oxygen extraction rises and blood flow is preferentially directed to the heart and brain.
When compensation fails, cerebral hypoxia, myocardial ischemia, lactic acidosis, hypotension, heart failure, altered mental status, seizures, and coma may occur.

The body can adapt much better to chronic anemia than to sudden blood loss. A person with slowly progressive anemia may remain awake at a hemoglobin concentration that would be life-threatening if reached abruptly.

Harrison notes that symptoms reflect impaired oxygen delivery, and tolerance depends substantially on chronicity and the individual’s underlying health status. Harrison’s Principles of Internal Medicine, 22e, “Approach to the Diagnosis of Anemia.”

Important causes

1. Acute severe blood loss

This is the commonest dangerous setting.

Gastrointestinal bleeding: hematemesis, melena, hematochezia
Obstetric hemorrhage: postpartum hemorrhage, ruptured ectopic pregnancy, placental causes
Trauma
Ruptured aneurysm
Surgical bleeding
Retroperitoneal hemorrhage
Massive hemoptysis

Key point: Hemoglobin may initially be normal after acute hemorrhage because whole blood, not only red cells, is lost. The concentration may fall after fluid redistribution or intravenous fluid resuscitation. Treat the patient, shock state, and bleeding source, not just the first Hb value.

2. Severe hemolysis

Acute autoimmune hemolytic anemia
Mismatched blood transfusion reaction
G6PD-deficiency-related oxidative hemolysis
Severe malaria
Microangiopathic hemolysis, such as TTP or DIC
Paroxysmal nocturnal hemoglobinuria, less commonly as an abrupt crisis

3. Marrow-production failure or severe chronic anemia

Aplastic anemia
Acute leukemia or marrow infiltration
Severe iron deficiency with cardiac decompensation
Severe vitamin B12 or folate deficiency
Chronic kidney disease with inadequate erythropoietin production

4. Anemia with a second cause of impaired consciousness

Anemia may lower cerebral oxygen reserve, while coma is actually precipitated by:

Hypoxemia or respiratory failure
Sepsis
Hypoglycemia
Uremia
Hepatic encephalopathy
Stroke, seizure, meningitis, encephalitis
Drug or alcohol intoxication
Carbon monoxide exposure
Cerebral malaria

Clinical features

Symptoms depend on the rate of onset, severity, age, and cardiovascular reserve.

Symptoms of anemia and cerebral hypoxia

Fatigue and weakness
Exertional dyspnea progressing to breathlessness at rest
Dizziness, presyncope, syncope
Headache
Poor concentration, confusion, agitation
Visual blurring
Drowsiness progressing to stupor or coma

Cardiovascular findings

Tachycardia
Bounding pulse initially, weak pulse in shock
Hypotension, especially with acute hemorrhage
Postural hypotension
Systolic flow murmur
Angina, myocardial ischemia, acute heart failure
Cold peripheries and delayed capillary refill in shock

Features suggesting the cause

Hematemesis/melena: upper gastrointestinal bleed
Vaginal bleeding: obstetric or gynecologic hemorrhage
Jaundice, dark urine, splenomegaly: hemolysis
Fever and altered consciousness after travel: severe malaria or sepsis
Petechiae/purpura: thrombocytopenia, DIC, leukemia, TTP
Bone pain, lymphadenopathy, hepatosplenomegaly: hematologic malignancy
Pancytopenia: marrow failure or infiltration

Emergency assessment and stabilization

Treat this as an ABCDE emergency.

A. Airway

Protect the airway in a patient with GCS ≤8, inability to protect airway, ongoing vomiting, or seizures.
Consider rapid-sequence intubation when required.

B. Breathing

Give high-concentration oxygen while assessing hypoxemia.
Check pulse oximetry and arterial/venous blood gas with lactate.
Remember: pulse oximetry can be normal in anemia because it measures saturation, not oxygen content.

C. Circulation

Place two wide-bore IV cannulas or obtain rapid central/intraosseous access.
Monitor ECG, blood pressure, oxygen saturation, temperature, urine output, and mental status.
Send blood immediately for:
- CBC with indices
- Reticulocyte count
- Peripheral blood film
- Blood group, antibody screen, and crossmatch
- PT/INR, aPTT, fibrinogen
- Urea, electrolytes, creatinine
- Liver tests, glucose
- LDH, bilirubin, haptoglobin, direct antiglobulin test if hemolysis is possible
- Lactate and blood gas
- Pregnancy test in relevant patients
- Malaria testing when clinically indicated

D. Disability

Record GCS, pupils, focal deficits, seizures, and capillary glucose.
Correct hypoglycemia immediately if present.
Do not assume coma is due to anemia when there are focal neurological signs or disproportionate coma.

E. Exposure and focused search for bleeding/cause

Look for external trauma, bruising, rash, jaundice, melena, rectal blood, vaginal bleeding, or abdominal distension.
Perform urgent bedside ultrasound or targeted imaging if internal bleeding is suspected.

Immediate treatment

1. Restore oxygen carrying capacity

Transfuse packed red blood cells urgently in severe symptomatic anemia with shock, hypoxia, ischemia, heart failure, syncope, or altered consciousness.
In life-threatening bleeding, activate the local major hemorrhage protocol. Red cells alone may be insufficient: plasma, platelets, fibrinogen replacement, and early hemorrhage control may be needed.
Do not delay life-saving transfusion while awaiting full crossmatch if the patient is unstable. Use emergency uncrossmatched blood according to local transfusion policy.

For stable, non-bleeding adults, restrictive transfusion practice is generally preferred: NICE advises considering a threshold of 70 g/L (7 g/dL) with a post-transfusion target of 70-90 g/L, but this rule does not replace urgent clinical judgment in active bleeding, shock, coma, or myocardial ischemia. NICE also recommends a single unit followed by reassessment for stable adults without active bleeding. See the NICE red-cell guidance.

2. Control the cause

Hemorrhage: direct pressure, endoscopy, surgery, interventional radiology, obstetric hemorrhage protocol, tranexamic acid where appropriate.
Hemolysis: stop the trigger, treat infection, manage transfusion reaction, use disease-specific treatment.
Severe malaria: urgent parenteral antimalarial therapy and critical-care support.
Marrow failure/leukemia: hematology consultation, transfusion support, treatment of infection and underlying disease.

3. Avoid treatment errors

Do not give excessive crystalloid fluid without reassessment: it can worsen dilutional anemia and pulmonary edema.
Do not use oral iron as emergency treatment for coma or hemodynamic instability.
Do not overlook hypoglycemia, infection, intracranial pathology, or intoxication.
In chronic severe anemia, transfuse carefully and reassess for fluid overload, particularly in elderly people and those with cardiac or renal disease.

Short exam answer

Anemic coma is coma due to critical reduction in cerebral oxygen delivery caused by severe, usually acute, anemia or anemia combined with another hypoxic or circulatory insult. It presents with pallor, tachycardia, hypotension or shock, dyspnea, altered mental status, and sometimes heart failure. It requires immediate ABCDE resuscitation, oxygen, IV access, blood grouping and crossmatch, urgent packed red-cell transfusion when clinically indicated, identification and control of bleeding or hemolysis, and exclusion of concomitant causes of coma such as hypoglycemia, sepsis, stroke, or cerebral malaria.

Q112. Normocytic normochromic anemia

Definition

Normocytic normochromic anemia is anemia in which red blood cells are normal in size and hemoglobin concentration:

MCV: approximately 80-100 fL
MCHC: normal
Peripheral film: red cells are generally normal in size and color, though other diagnostic abnormalities may be present.

It is a morphologic description, not a diagnosis.

Common causes include acute hemorrhage, hemolysis, renal disease, anemia of chronic inflammation, marrow hypoplasia, and marrow infiltration. Henry’s Clinical Diagnosis and Management by Laboratory Methods, “Normocytic Anemia.”

Core concept: classify by marrow response

The most useful initial discriminator is the reticulocyte response.

Reticulocyte calculations

Absolute reticulocyte count

[ Absolute\ reticulocyte\ count = Reticulocyte% \times RBC\ count ]

Corrected reticulocyte count

[ Corrected\ retic% = Retic% \times \frac{Patient\ hematocrit}{45} ]

Reticulocyte production index, RPI

[ RPI = \frac{Corrected\ retic%}{Maturation\ correction\ factor} ]

A low hematocrit causes premature reticulocytes to circulate longer, so the raw reticulocyte percentage can be misleadingly high. The RPI corrects for both anemia severity and prolonged reticulocyte maturation.

RPI >2-3: adequate marrow response, suggesting blood loss or hemolysis
RPI <2: inadequate production, suggesting hypoproliferative anemia

Quick Compendium of Clinical Pathology, section 4.4.1.3, gives the corrected reticulocyte count and RPI formulas. Henry’s Clinical Diagnosis and Management by Laboratory Methods states that an RPI above 2 points principally toward acute blood loss or hemolysis.

Classification

Group	Reticulocyte response	Main possibilities
Hyperproliferative normocytic anemia	Increased RPI, usually >2	Acute blood loss, hemolysis
Hypoproliferative normocytic anemia	Low/inappropriately normal RPI	Chronic kidney disease, inflammation, endocrine disease, marrow failure, marrow infiltration, pure red-cell aplasia
Mixed/dimorphic anemia	Variable MCV, high RDW often	Iron deficiency plus B12/folate deficiency, recent transfusion, combined disease

A. Hyperproliferative normocytic anemia

1. Acute blood loss

Examples:

Trauma
Gastrointestinal hemorrhage
Postpartum hemorrhage
Ruptured ectopic pregnancy
Surgery
Retroperitoneal bleeding

Findings

Initial MCV is typically normal.
Hemoglobin can be initially misleadingly normal.
Reticulocytosis appears after several days if marrow function and iron supply are adequate.
Shock features may predominate: tachycardia, hypotension, cool extremities, oliguria, elevated lactate.

With time, persistent blood loss produces iron deficiency and the anemia becomes microcytic.

2. Hemolytic anemia

Hemolysis is accelerated destruction of red cells.

Laboratory pattern

Increased reticulocyte count
Increased unconjugated bilirubin
Increased LDH
Low haptoglobin
Polychromasia on smear
Hemoglobinuria/hemosiderinuria in intravascular hemolysis
Direct antiglobulin test positive in immune hemolysis

Smear clues

Smear finding	Important association
Spherocytes	Autoimmune hemolysis, hereditary spherocytosis
Schistocytes	DIC, TTP/HUS, mechanical valve, severe hypertension
Bite cells/Heinz bodies	G6PD deficiency, oxidant stress
Sickle cells	Sickle-cell disease
Agglutination	Cold agglutinin disease
Teardrop cells, nucleated RBCs	Marrow infiltration or myelofibrosis

A positive direct antiglobulin test supports immune hemolysis. If hemolysis is present but the test is negative, consider membrane defects, enzyme defects, hemoglobinopathies, mechanical hemolysis, microangiopathic disease, burns, infection, and toxins.

B. Hypoproliferative normocytic anemia

1. Anemia of chronic inflammation or chronic disease

This occurs in chronic infection, autoimmune disease, inflammatory bowel disease, cancer, and other chronic inflammatory states.

Mechanism

Inflammation increases hepcidin, which:

Reduces intestinal iron absorption
Traps iron in macrophages and hepatocytes
Reduces iron availability for erythropoiesis

Inflammation also:

Reduces erythropoietin production and marrow response
Shortens red-cell survival

Typical laboratory pattern

Low serum iron
Low transferrin/TIBC
Normal or high ferritin
Low transferrin saturation
Raised CRP/ESR
Low reticulocyte response
Usually normocytic, sometimes mildly microcytic

2. Chronic kidney disease

Mechanism

Inadequate renal erythropoietin production
Reduced red-cell survival
Functional iron deficiency due to inflammation/hepcidin
Uremic suppression of marrow function
Blood loss from dialysis or investigations in some patients

Findings

Normocytic normochromic anemia
Low reticulocyte response
Reduced eGFR/raised creatinine
Iron deficiency may coexist

Management includes correction of iron deficiency, erythropoiesis-stimulating agents in appropriate patients, and transfusion only when clinically necessary.

3. Endocrine causes

Hypothyroidism
Hypopituitarism
Adrenal insufficiency
Hyperparathyroidism

Endocrine disorders may produce a mild normocytic normochromic anemia through reduced erythropoietic drive.

4. Bone marrow failure or suppression

Aplastic anemia
Chemotherapy or radiotherapy
Drugs: for example, cytotoxic drugs, chloramphenicol, some anticonvulsants
Alcohol toxicity
Viral infections, including parvovirus B19
Severe systemic illness

Clues

Low reticulocyte count
Pancytopenia if multiple cell lines are affected
Hypocellular marrow in aplastic anemia

5. Bone marrow infiltration or replacement

Acute leukemia
Lymphoma
Multiple myeloma
Myelofibrosis
Metastatic carcinoma
Granulomatous disease

Clues

Leukoerythroblastic film
Nucleated RBCs
Immature granulocytes
Teardrop cells
Hepatosplenomegaly
Bone pain or constitutional symptoms

6. Pure red-cell aplasia

Characterized by:

Severe normocytic anemia
Marked reticulocytopenia
Absence or near-absence of erythroid precursors in an otherwise relatively preserved marrow

Causes include autoimmune disease, thymoma, parvovirus B19, drugs, and lymphoproliferative disorders.

7. Early nutritional deficiency or mixed anemia

Early iron deficiency may still be normocytic. Conversely, combined iron deficiency and vitamin B12/folate deficiency may yield an apparently normal MCV despite marked disease. A raised RDW and abnormal smear are useful clues.

Diagnostic approach

Step 1: Confirm and characterize anemia

Order:

CBC: Hb, hematocrit, RBC count, MCV, MCHC, RDW
Reticulocyte count and RPI
Peripheral smear

Harrison emphasizes that history, examination, blood-film review, and reticulocyte count are foundational in anemia assessment. Harrison’s Principles of Internal Medicine, 22e, “Approach to the Diagnosis of Anemia.”

Step 2: Determine whether reticulocytes are high or low

If RPI is high

Think:

Acute bleeding
Hemolysis

Tests:

Stool or other evaluation for bleeding source
LDH, bilirubin, haptoglobin
Direct antiglobulin test
Urinalysis for blood/hemoglobin
G6PD assay when relevant
Hemoglobin electrophoresis
Coagulation tests and renal function
Smear review

If RPI is low

Think impaired production.

Tests:

Ferritin, serum iron, transferrin saturation, TIBC
CRP/ESR
Creatinine/eGFR
Liver tests
TSH
Vitamin B12 and folate if clinical suspicion or high RDW
Serum protein electrophoresis where myeloma is possible
Viral testing when indicated
Bone marrow aspiration/biopsy if unexplained, persistent, severe, or accompanied by leukopenia/thrombocytopenia or abnormal smear

Management principles

Treatment is directed at the cause:

Acute blood loss: resuscitation, stop bleeding, transfuse when required.
Hemolysis: treat the specific mechanism.
Chronic kidney disease: iron assessment/repletion, ESA where indicated, manage renal disease.
Inflammation: treat underlying infection, autoimmune disease, malignancy, or inflammatory disorder.
Marrow failure/infiltration: urgent hematology referral and disease-specific therapy.
Nutritional deficiency: replace the deficient nutrient and identify the source.

Avoid giving empiric iron indefinitely without evidence of iron deficiency, especially in a normocytic anemia with elevated ferritin or inflammation.

Short exam answer

Normocytic normochromic anemia is anemia with normal MCV and MCHC. It is classified by the reticulocyte response. A high reticulocyte production index suggests acute blood loss or hemolysis; a low index indicates impaired marrow production, as in chronic kidney disease, anemia of inflammation, endocrine disease, marrow aplasia, marrow infiltration, or pure red-cell aplasia. Evaluation includes CBC, reticulocyte index, peripheral smear, renal function, iron studies, inflammatory markers, hemolysis profile, and bone marrow study when indicated.

Q180. Differential diagnosis of anemic syndrome

Definition of anemic syndrome

Anemic syndrome is the clinical and laboratory manifestation of reduced circulating red-cell mass and reduced oxygen-carrying capacity of blood.

It is not synonymous with a particular hemoglobin number. The clinical impact depends on:

Severity of anemia
Rapidity of onset
Age
Pregnancy status
Cardiac and pulmonary reserve
Presence of sepsis, hypoxemia, or vascular disease
Cause of anemia

Clinical manifestations

General symptoms

Fatigue, weakness, reduced exercise tolerance
Dyspnea on exertion
Palpitations
Dizziness, headache, tinnitus
Reduced concentration and irritability
Syncope in severe or acute anemia

Signs

Pallor of conjunctivae, tongue, palmar creases, nail beds
Tachycardia and systolic flow murmur
Postural hypotension
Tachypnea
Heart failure in severe anemia or underlying cardiac disease
Cognitive dysfunction, confusion, or coma in critical states

Etiologic clues

Feature	Differential implication
Pica, koilonychia, glossitis	Iron deficiency
Jaundice, splenomegaly, dark urine	Hemolysis
Neuropathy, loss of vibration sense, glossitis	Vitamin B12 deficiency
Diarrhea, weight loss	Malabsorption, celiac disease, IBD, malignancy
Melena/hematochezia	Gastrointestinal blood loss
Menorrhagia	Gynecologic blood loss
Fever, night sweats, weight loss	Infection, lymphoma, leukemia, malignancy
Bone pain	Myeloma, marrow infiltration
Petechiae/infections plus anemia	Marrow failure, leukemia
Renal symptoms	Chronic kidney disease
Alcohol use/liver signs	Folate deficiency, liver disease, marrow toxicity
Family history/ethnic background	Hemoglobinopathy, membrane/enzyme disorder

Broad etiologic classification

There are three fundamental mechanisms.

1. Reduced red-cell production

The marrow does not produce enough RBCs.

Examples:

Iron deficiency
Vitamin B12 deficiency
Folate deficiency
Anemia of chronic inflammation
Chronic kidney disease with reduced erythropoietin
Aplastic anemia
Myelodysplastic syndrome
Bone marrow infiltration
Endocrine disorders
Drug, alcohol, toxin, or radiation effect
Infection-associated marrow suppression

2. Increased red-cell loss

Acute blood loss
Chronic occult blood loss
Menstrual loss
Gastrointestinal blood loss
Urinary or pulmonary blood loss

3. Increased red-cell destruction: hemolysis

Inherited: sickle-cell disease, thalassemia, hereditary spherocytosis, G6PD deficiency, pyruvate kinase deficiency
Acquired: autoimmune hemolysis, microangiopathic hemolysis, DIC, mechanical valve hemolysis, malaria, burns, drugs, PNH

Morphologic differential diagnosis by MCV

A. Microcytic anemia: MCV <80 fL

Cause	Typical clues	Key tests
Iron deficiency anemia	Blood loss, pregnancy, poor intake, pica, high RDW	Low ferritin, low serum iron, high TIBC
Thalassemia	Family/ethnic history, disproportionate microcytosis, normal/high RBC count	Hb electrophoresis, genetic testing if needed
Anemia of inflammation	Chronic disease, mild microcytosis possible	Low iron, low TIBC, normal/high ferritin
Sideroblastic anemia	Alcohol, drugs, MDS, toxins	High iron/ferritin, marrow ring sideroblasts
Lead poisoning	Exposure, abdominal/neuro symptoms	Blood lead level, basophilic stippling

B. Normocytic anemia: MCV 80-100 fL

Reticulocyte response	Differential
High	Acute hemorrhage, hemolysis
Low	CKD, inflammation, endocrine disease, marrow failure, marrow infiltration, early iron deficiency, mixed nutritional deficiency, pure red-cell aplasia

C. Macrocytic anemia: MCV >100 fL

Category	Causes
Megaloblastic	Vitamin B12 deficiency, folate deficiency, antifolate/antimetabolite drugs, myelodysplasia
Non-megaloblastic	Alcohol use, liver disease, hypothyroidism, reticulocytosis, pregnancy, marrow disorders

Blood film helps distinguish them:

Macro-ovalocytes and hypersegmented neutrophils: megaloblastic process
Round macrocytes: often alcohol/liver disease
Polychromasia: reticulocytosis/hemolysis

A practical stepwise differential diagnosis

Step 1: Confirm true anemia

Obtain:

CBC with Hb, hematocrit, RBC indices, RDW
Compare with prior Hb values
Consider dilutional anemia from pregnancy, fluid overload, or recent IV fluids

Step 2: Assess urgency

Look for:

Active bleeding
Shock
Chest pain or myocardial ischemia
Hypoxia
Syncope or altered consciousness
Acute heart failure
Severe thrombocytopenia or neutropenia
Fever with suspected hemolysis or sepsis

These patients need urgent stabilization before an extended etiologic workup.

Step 3: Classify by MCV and blood film

The peripheral smear is often diagnostically decisive.

Blood-film feature	Differential
Hypochromia, pencil cells	Iron deficiency
Target cells	Thalassemia, liver disease, hemoglobinopathy
Spherocytes	Hereditary spherocytosis, autoimmune hemolysis
Schistocytes	TTP, HUS, DIC, mechanical hemolysis
Bite cells	G6PD deficiency
Basophilic stippling	Lead toxicity, thalassemia, sideroblastic anemia
Hypersegmented neutrophils	B12/folate deficiency
Teardrop cells/leukoerythroblastosis	Myelofibrosis or marrow infiltration
Blasts	Acute leukemia
Rouleaux	Plasma-cell dyscrasia, chronic inflammation

Step 4: Use reticulocyte response

High reticulocytes: hemorrhage or hemolysis
Low reticulocytes: reduced production

This separates anemia caused by peripheral loss/destruction from anemia caused by marrow underproduction.

Step 5: Use targeted tests

Tests for iron-restricted erythropoiesis

Ferritin
Serum iron
Transferrin/TIBC
Transferrin saturation
CRP/ESR when ferritin may be raised by inflammation

Tests for hemolysis

LDH
Unconjugated bilirubin
Haptoglobin
Urinalysis
Direct antiglobulin test
Peripheral smear

Tests for nutritional anemia

Vitamin B12
Folate
Methylmalonic acid, if B12 result is uncertain
Homocysteine, if needed

Tests for systemic disease

Renal function/eGFR
Liver enzymes
TSH
CRP/ESR
Serum protein electrophoresis and free-light chains if plasma-cell dyscrasia suspected
Viral or autoimmune testing where clinically appropriate

Tests for blood loss

Menstrual and obstetric history
Stool testing and endoscopic evaluation when indicated
Urinalysis
Gynecologic assessment
Imaging for internal bleeding when appropriate

Bone marrow examination

Indications include:

Unexplained persistent anemia
Pancytopenia or bicytopenia
Blasts, teardrop cells, nucleated RBCs, or leukoerythroblastic film
Suspected leukemia, MDS, aplastic anemia, infiltration, or hematologic malignancy

Distinguishing common anemias

Finding	Iron deficiency	Anemia of inflammation	Hemolysis	CKD anemia	B12/folate deficiency
MCV	Low, late stage	Usually normal, sometimes low	Normal or high due to reticulocytes	Normal	High
Reticulocytes	Low	Low	High	Low	Low
Ferritin	Low	Normal/high	Normal/high	Normal/high, variable	Normal/high
TIBC	High	Low	Normal	Normal/low	Normal
LDH	Usually normal	Normal	High	Normal/slightly high	Can be very high
Bilirubin	Normal	Normal	Indirect bilirubin high	Normal	May be mildly high
Haptoglobin	Normal	Normal	Low	Normal	Normal
Main clue	Blood loss/pica	Chronic inflammatory disorder	Jaundice, dark urine, splenomegaly	Renal impairment	Glossitis, neuropathy or malabsorption

Important diagnostic traps

Normal MCV does not exclude nutritional deficiency.
Combined iron deficiency plus B12/folate deficiency can yield a normal average MCV. Check RDW and film.
Ferritin can be falsely normal or high in inflammation.
Ferritin is an acute-phase reactant. Interpret it with CRP/ESR, transferrin saturation, and clinical context.
A low Hb after IV fluid may be dilutional.
Assess volume status and bleeding history.
A normal reticulocyte percentage can be inappropriately low in severe anemia.
Use absolute reticulocyte count or RPI.
Hemolysis can coexist with impaired marrow response.
Reticulocytosis may be absent in hemolysis if iron, folate, B12, or marrow reserve is inadequate.
Unexplained iron deficiency in an adult man or postmenopausal woman requires evaluation for gastrointestinal blood loss or malignancy.
Do not label anemia of chronic disease without excluding iron deficiency and other treatable causes.

Exam-style concluding framework

The differential diagnosis of anemic syndrome begins with confirmation of anemia, assessment of urgency, MCV-based classification, reticulocyte response, and peripheral-blood-film examination. Anemia is then categorized as reduced production, blood loss, or increased destruction. Microcytic anemia suggests iron deficiency, thalassemia, inflammation, sideroblastic anemia, or lead toxicity; normocytic anemia suggests acute blood loss, hemolysis, renal disease, inflammation, or marrow disease; macrocytic anemia suggests B12/folate deficiency, alcohol/liver disease, hypothyroidism, reticulocytosis, drugs, or myelodysplasia. Targeted iron studies, hemolysis testing, renal/endocrine assessment, nutritional assays, evaluation for bleeding, and bone marrow examination when indicated establish the cause.

Recent-evidence note: recent transfusion meta-analyses, including PMID 38411260, focus on specific high-risk groups such as acute myocardial infarction. They do not support using a single hemoglobin threshold without considering bleeding, symptoms, ischemia, and overall clinical status.

Explain Q120: microcytic hypochromic anemia

Reading File

Finding Sources

Searching PubMed

"Iron Deficiency Anemia"[MeSH Terms] AND "Diagnosis"[MeSH Terms]

Searching the Web

British Society Haematology guideline iron deficiency anaemia diagnosis ferritin adults

Q120. Hypochromic microcytic anemia

Definition

Microcytic hypochromic anemia is anemia in which red cells are:

Microcytic: smaller than normal, usually MCV <80 fL in adults
Hypochromic: contain less hemoglobin, reflected by a low MCH and often reduced MCHC
On blood film, cells show an enlarged central pale area

It results from impaired hemoglobin synthesis. It is a morphologic pattern, not a final diagnosis.

The major causes are:

Iron deficiency anemia - the most common cause
Anemia of chronic inflammation/disease
Thalassemia
Sideroblastic anemia
Lead poisoning
Rare disorders of iron transport or heme synthesis

Henry’s Clinical Diagnosis and Management by Laboratory Methods, “Microcytic Anemia,” identifies iron deficiency, chronic disease, thalassemia, and sideroblastic anemia as the principal causes.

Normal physiology: why iron deficiency causes microcytosis

Hemoglobin consists of:

Heme, which contains iron
Globin chains

When hemoglobin synthesis is reduced, erythroblasts continue dividing before adequate hemoglobin has accumulated. This produces smaller erythrocytes with less hemoglobin:

smaller cells: low MCV
paler cells: low MCH/MCHC
variable-sized cells in evolving iron deficiency: high RDW

Microcytosis may be marked even when anemia is only moderate, particularly in thalassemia trait.

Causes and pathogenesis

1. Iron deficiency anemia

Causes

Iron deficiency occurs when iron loss or demand exceeds intake and absorption.

A. Chronic blood loss

This is the most important cause in adults.

Gastrointestinal blood loss

Peptic ulcer disease
Gastritis, including NSAID-related injury
Colorectal cancer
Gastric cancer
Esophagitis
Angiodysplasia
Inflammatory bowel disease
Hookworm infestation
Hemorrhoids, though do not assume these are the only cause without assessment

Gynecologic and obstetric blood loss

Heavy menstrual bleeding
Fibroids
Endometriosis
Postpartum blood loss
Repeated pregnancies

Other

Frequent blood donation
Hematuria
Recurrent epistaxis
Pulmonary hemosiderosis, rarely

B. Reduced iron intake

Malnutrition
Restricted diets with poor iron content
Infants receiving excessive cow’s milk
Elderly or socially vulnerable patients

C. Reduced absorption

Celiac disease
Atrophic gastritis
Helicobacter pylori infection in selected cases
Bariatric surgery
Gastrectomy
Crohn disease affecting the proximal small bowel
Long-term acid suppression can contribute in some settings

D. Increased requirements

Pregnancy
Lactation
Infancy and adolescence
Periods of rapid growth

Clinical features of iron deficiency

General features of anemia

Fatigue
Reduced exercise capacity
Dyspnea on exertion
Palpitations
Dizziness, headache, syncope when severe
Pallor
Tachycardia and systolic flow murmur

Features more suggestive of iron deficiency

Pica, especially pagophagia, craving ice
Brittle nails
Koilonychia, spoon-shaped nails
Atrophic glossitis
Angular cheilitis
Hair loss
Restless legs symptoms
Poor concentration and impaired school/work performance

Long-standing iron deficiency may cause Plummer-Vinson syndrome: dysphagia, iron deficiency anemia, and esophageal webs.

Laboratory findings in iron deficiency anemia

Test	Typical result
Hemoglobin/hematocrit	Reduced
MCV	Low, often late in early deficiency
MCH/MCHC	Low
RDW	Usually high
Reticulocyte count	Low or inappropriately normal
Serum ferritin	Low
Serum iron	Low
TIBC/transferrin	High
Transferrin saturation	Low, often <20%
Blood film	Microcytosis, hypochromia, anisocytosis, poikilocytosis, pencil cells/elliptocytes
Bone marrow iron stain	Absent stores, rarely needed

Stages of iron depletion

Depletion of iron stores
- Ferritin falls first
- Hemoglobin and MCV may still be normal
Iron-deficient erythropoiesis
- Serum iron and transferrin saturation fall
- TIBC rises
- RDW may increase
Iron deficiency anemia
- Hemoglobin falls
- Hypochromia and microcytosis become apparent

A low ferritin strongly supports depleted iron stores. However, ferritin is an acute-phase reactant and may be falsely normal or elevated in inflammation, chronic kidney disease, liver disease, malignancy, and infection.

The British Society for Haematology laboratory guidance supports using CBC morphology and iron studies together rather than relying on one isolated test.

Current ferritin interpretation

Thresholds vary by clinical setting and laboratory. In an otherwise healthy adult, a ferritin ≤30 ng/mL (µg/L) is commonly used to support iron deficiency. In active inflammation, ferritin alone is insufficient; transferrin saturation and inflammatory markers should be assessed. Recent ASH guidance discusses higher ferritin thresholds in inflammatory states, with iron deficiency possible if ferritin is under 100 ng/mL or transferrin saturation is under 20%, depending on the clinical setting. See the ASH diagnostic update.

2. Anemia of chronic inflammation

This is also called anemia of chronic disease. It is often normocytic at first, but prolonged disease can become mildly microcytic and hypochromic.

Causes

Chronic infection, such as tuberculosis, osteomyelitis, or endocarditis
Autoimmune disease, such as rheumatoid arthritis or systemic lupus erythematosus
Inflammatory bowel disease
Chronic kidney disease
Malignancy
Chronic heart failure and other chronic inflammatory states

Mechanism

Inflammatory cytokines increase hepatic production of hepcidin. Hepcidin inhibits ferroportin, the iron-export protein on enterocytes and macrophages. This causes:

Reduced intestinal iron absorption
Reduced release of stored iron from macrophages
Reduced circulating iron available for erythropoiesis
Reduced response to erythropoietin
Reduced erythrocyte survival

The patient may have adequate or increased total body iron but inadequate iron availability to the marrow, termed functional iron deficiency.

Laboratory pattern

Test	Anemia of inflammation
Serum iron	Low
TIBC/transferrin	Low or normal
Ferritin	Normal or increased
Transferrin saturation	Low
CRP/ESR	Often increased
Reticulocytes	Low
MCV	Usually normal, sometimes mildly low

3. Thalassemia

Thalassemias are inherited disorders with reduced synthesis of alpha or beta globin chains.

Types

Alpha-thalassemia
Beta-thalassemia

Clinical severity ranges from asymptomatic trait to severe transfusion-dependent disease.

Typical clues

Family history of anemia
Ethnic background associated with higher prevalence: Mediterranean, Middle Eastern, South Asian, Southeast Asian, African ancestry
Marked microcytosis out of proportion to the degree of anemia
Relatively high or normal RBC count despite low MCV
Target cells on peripheral smear
Normal iron stores unless iron deficiency coexists
Splenomegaly in more severe disease

Laboratory distinction from iron deficiency

Finding	Iron deficiency anemia	Thalassemia trait
RBC count	Often low or normal	Often normal or high
MCV	Low	Often very low
RDW	Often high	Often normal or mildly high
Ferritin	Low	Normal
Blood film	Pencil cells, anisopoikilocytosis	Target cells, marked microcytosis
Hb electrophoresis	Usually normal	Beta-thal trait: HbA2 often raised
Response to iron	Improves if adherent and cause corrected	No correction unless iron deficiency also exists

Mentzer index

[ \text{Mentzer index} = \frac{MCV}{RBC\ count\ (millions/\mu L)} ]

>13 favors iron deficiency anemia
<13 favors thalassemia trait

It is only a screening aid. It does not replace iron studies and hemoglobin analysis.

Important caution

Do not prescribe long-term iron solely because a patient has microcytosis. Confirm iron deficiency first. People with thalassemia trait may be mistakenly treated with iron for years.

4. Sideroblastic anemia

Sideroblastic anemia results from defective incorporation of iron into heme. Iron is present but cannot be properly utilized, so it accumulates in erythroid precursors.

Causes

Congenital

Most commonly X-linked ALAS2-related sideroblastic anemia

Acquired

Myelodysplastic syndromes
Alcohol excess
Lead toxicity
Vitamin B6 deficiency
Copper deficiency
Drugs: isoniazid, linezolid, chloramphenicol, some chemotherapeutic agents
Zinc excess causing copper deficiency

Findings

Microcytic, normocytic, or occasionally macrocytic anemia
Increased serum iron
Increased ferritin
Increased transferrin saturation
Dimorphic blood film may occur
Bone marrow shows ring sideroblasts with Prussian blue iron stain

A ring sideroblast is an erythroblast containing iron-laden mitochondria arranged around the nucleus.

5. Lead poisoning

Lead impairs heme synthesis and can cause microcytic hypochromic anemia.

Sources

Occupational exposure
Contaminated paint, dust, soil, water, or traditional remedies
Battery manufacturing and recycling
Firing ranges
Exposure in children from old painted homes

Features

Abdominal pain or constipation
Neurocognitive or behavioral changes
Peripheral neuropathy, classically wrist or foot drop in severe adult exposure
Renal dysfunction
Hypertension
In children: developmental and learning impairment

Laboratory clues

Microcytic hypochromic anemia
Coarse basophilic stippling on smear, though absence does not exclude lead exposure
Elevated blood lead concentration
Elevated zinc protoporphyrin may be supportive

Diagnostic approach to a patient with microcytic hypochromic anemia

Step 1: Confirm morphology

Order:

CBC with Hb, MCV, MCH, MCHC, RDW, RBC count
Reticulocyte count
Peripheral blood film

Typical film findings include microcytosis, hypochromia, anisocytosis, poikilocytosis, and pencil cells in iron deficiency.

Step 2: Check iron status first

The first-line tests are:

Ferritin
Serum iron
Transferrin or TIBC
Transferrin saturation
CRP or ESR if inflammation is possible

Interpretation table

Test	Iron deficiency	Chronic inflammation	Thalassemia	Sideroblastic anemia
Ferritin	Low	Normal/high	Normal	High
Serum iron	Low	Low	Normal/high	High
TIBC/transferrin	High	Low/normal	Normal	Normal/low
Transferrin saturation	Low	Low	Normal/high	High
RBC count	Low/normal	Low/normal	Normal/high	Variable
RDW	High	Usually normal/slightly high	Often normal	Often high
Blood film	Pencil cells	Mild microcytosis	Target cells	Dimorphic population, stippling possible
Bone-marrow iron	Absent	Present/increased in macrophages	Normal	Ring sideroblasts

Step 3: Identify the cause of confirmed iron deficiency

Finding iron deficiency is not the endpoint. The cause must be found.

History

Menstrual pattern and pregnancy history
Dietary intake
Blood donation
NSAID, aspirin, anticoagulant use
Melena, hematochezia, abdominal pain, dyspepsia, altered bowel habit
Weight loss, dysphagia, diarrhea
Celiac disease symptoms
Family history of colorectal or gastric cancer
Alcohol, drug, occupational, and lead exposure

Examination

Pallor, tachycardia, signs of heart failure
Glossitis, cheilitis, koilonychia
Abdominal mass or hepatosplenomegaly
Rectal examination where appropriate
Pelvic/gynecologic assessment when heavy menstrual bleeding is suspected

Further evaluation

Celiac disease serology when appropriate
Urinalysis for hematuria
Gynecologic assessment for heavy menstrual bleeding
Gastrointestinal investigation based on risk profile

In adult men and postmenopausal women, unexplained iron deficiency anemia warrants evaluation for gastrointestinal blood loss, including malignancy when appropriate. A recent systematic review, PMID 38977142, evaluated fecal immunochemical testing as a tool to improve colonoscopy triage in people with iron deficiency, but it does not replace clinical assessment and definitive evaluation when indicated.

Management

1. Treat the underlying cause

Examples:

Heavy menstrual bleeding: gynecologic treatment plus iron replacement
Peptic ulcer or NSAID injury: stop offending drug when possible and treat lesion
Celiac disease: gluten-free diet plus iron replacement
Colon cancer: urgent appropriate oncologic and surgical assessment
Hookworm: antiparasitic therapy
Chronic inflammatory disease: control inflammation and assess for coexisting absolute iron deficiency
Lead poisoning: remove exposure and use specialist-directed chelation when indicated
Sideroblastic anemia: remove cause, correct B6/copper deficiency where appropriate, manage MDS with hematology

2. Iron replacement in iron deficiency anemia

Oral iron

Suitable when the patient is stable, can absorb oral medication, and does not need immediate correction.

Common approaches use ferrous salts, providing a lower or moderate dose of elemental iron daily or on alternate days. Adverse effects include nausea, epigastric discomfort, constipation, diarrhea, and dark stools.

Practical points:

Take away from calcium, tea, coffee, and antacids when possible.
Vitamin C is not routinely necessary for everyone.
A reticulocyte response generally appears within about 1 week if absorption and adherence are adequate.
Hemoglobin should rise over subsequent weeks.
Continue therapy after hemoglobin normalizes to restore iron stores, with duration guided by the cause and follow-up ferritin.

Intravenous iron

Consider when:

Oral iron is not tolerated
Malabsorption is present
There is ongoing loss exceeding oral replacement
Rapid repletion is clinically needed but there is no indication for emergency RBC transfusion
Chronic kidney disease or inflammatory bowel disease makes oral therapy ineffective or unsuitable

Red-cell transfusion

Transfusion is not routine treatment for uncomplicated iron deficiency. Consider it when anemia is severe and causes hemodynamic instability, active ischemia, heart failure, syncope, altered consciousness, or ongoing major bleeding. It must be accompanied by treatment of the iron deficit and cause of blood loss.

Complications

Untreated severe iron deficiency may lead to:

Poor exercise tolerance and reduced quality of life
Cognitive and developmental effects in children
Pregnancy complications
Cardiac strain and high-output heart failure in severe chronic anemia
Increased perioperative risk
Missed gastrointestinal or gynecologic disease, including malignancy

Short exam answer

Microcytic hypochromic anemia is anemia with reduced MCV and reduced hemoglobin content of erythrocytes. It results from defective hemoglobin synthesis. The common causes are iron deficiency anemia, anemia of chronic inflammation, thalassemia, sideroblastic anemia, and lead poisoning. The initial evaluation includes CBC, peripheral smear, reticulocyte count, ferritin, serum iron, TIBC/transferrin, transferrin saturation, and inflammatory markers. Low ferritin with high TIBC strongly suggests iron deficiency, whereas low iron with low TIBC and normal or high ferritin suggests anemia of inflammation. A high RBC count with marked microcytosis and normal iron stores suggests thalassemia. Management requires iron replacement only when deficiency is confirmed and, most importantly, investigation and treatment of the underlying cause.

Explain Q81: thalassemia versus sickle-cell disease

Reading File

Finding Sources

Searching Images

peripheral blood smear comparison sickle cells versus thalassemia target cells

Searching PubMed

"Sickle Cell Disease"[MeSH Terms] AND "Thalassemia"[MeSH Terms]

Searching the Web

American Society Hematology sickle cell disease guidelines hydroxyurea transfusion 2025 thalassemia guidelines

Your credits are exhausted. You can purchase a top-up or subscribe to a plan to continue using Orris. If you're already subscribed, your daily credits will reset tomorrow.

This is a shared conversation. Sign in to Orris to start your own chat.