A 30-year-old woman presents with fatigue, jaundice, and dark urine. She has a history of systemic lupus erythematosus. Blood tests show: Hb 7 g/dL, MCV 105 fL, reticulocyte count 12%, LDH elevated, indirect bilirubin elevated, haptoglobin undetectable. Peripheral smear shows spherocytes and polychromasia. Direct Coombs test (DAT) is POSITIVE. What is the diagnosis?	DIAGNOSIS: Warm Autoimmune Hemolytic Anemia (AIHA) — Secondary to SLE. HOW TO ARRIVE: The key clues are (1) acquired hemolytic anemia with spherocytes on smear, (2) POSITIVE Direct Antiglobulin Test (DAT/Coombs), which confirms antibody-coated RBCs, (3) underlying autoimmune disease (SLE). The elevated reticulocyte count, indirect hyperbilirubinemia, elevated LDH, and absent haptoglobin all confirm extravascular hemolysis. The DAT positivity is the diagnostic hallmark that separates autoimmune hemolysis from all other causes.

A 65-year-old man is admitted with severe fatigue and jaundice in winter. He reports that his fingers turn blue and painful in cold weather (Raynaud's phenomenon). Hb is 6 g/dL. Peripheral smear shows RBC agglutination. DAT is positive for complement (C3d) but negative for IgG. Cold agglutinin titer is markedly elevated. What is the diagnosis?	DIAGNOSIS: Cold Agglutinin Disease (Cold AIHA — IgM-mediated). HOW TO ARRIVE: The triad is (1) hemolytic anemia worse in cold, (2) RBC agglutination on peripheral smear (clumping), (3) DAT positive for C3d only (NOT IgG). IgM antibodies activate complement at cold temperatures but dissociate at 37°C, leaving only complement (C3d) on the RBC surface. Raynaud's in a patient with hemolytic anemia strongly points to cold agglutinin disease.

A 4-year-old child is brought with sudden pallor and jaundice after being given co-trimoxazole for a urinary tract infection. Hb drops to 5 g/dL. Peripheral smear shows Heinz bodies on crystal violet stain and bite cells (degmacytes). Reticulocytes are elevated. DAT is NEGATIVE. What is the diagnosis?	DIAGNOSIS: Drug-Induced Hemolytic Anemia due to G6PD Deficiency (but presented as drug-induced hemolytic anemia here — see key distinguisher). HOW TO ARRIVE: Heinz bodies (denatured Hb) and bite cells (macrophages removing Heinz bodies) are the hallmarks of oxidative hemolysis. The DAT is NEGATIVE, ruling out autoimmune cause. The trigger is a drug known to cause oxidative stress. Note: If DAT were positive, it would be drug-induced immune hemolytic anemia; with DAT negative + Heinz bodies, think G6PD or oxidative drug hemolysis.

A 25-year-old woman presents with pallor and mild jaundice. She has no drug exposure, no infections recently. Blood shows Hb 8 g/dL, reticulocytosis, elevated indirect bilirubin, elevated LDH, low haptoglobin. DAT is POSITIVE for IgG (warm antibody). No underlying autoimmune disease is found after full workup. What is the diagnosis?	DIAGNOSIS: Primary (Idiopathic) Warm Autoimmune Hemolytic Anemia. HOW TO ARRIVE: Warm AIHA = positive DAT for IgG + hemolytic picture (reticulocytosis, indirect hyperbilirubinemia, low haptoglobin, spherocytes on smear). When secondary causes (SLE, lymphoma, CLL, drugs) are excluded, it is labeled idiopathic/primary warm AIHA. IgG is the antibody type; it works best at 37°C (warm). It causes extravascular hemolysis in the spleen.

An elderly man with CLL develops increasing fatigue. CBC shows Hb 6 g/dL with reticulocytosis. Peripheral smear shows spherocytes. DAT is positive for IgG. What is the diagnosis?	DIAGNOSIS: Warm Autoimmune Hemolytic Anemia — Secondary to Chronic Lymphocytic Leukemia (CLL). HOW TO ARRIVE: CLL is the most common malignancy associated with warm AIHA. The malignant B-cells produce autoantibodies against RBCs. Positive DAT for IgG + hemolytic picture in a patient with CLL = secondary warm AIHA. The underlying cause (CLL) must always be identified because treating the CLL may resolve the AIHA.

A 25-year-old African-American man develops sudden-onset dark urine, pallor, and jaundice 2 days after starting primaquine for malaria prophylaxis. CBC shows Hb 7 g/dL, reticulocytosis. Peripheral smear shows Heinz bodies (on supravital stain) and bite cells. DAT is negative. Haptoglobin is undetectable. What is the diagnosis?	DIAGNOSIS: G6PD Deficiency — Drug-Triggered Hemolytic Crisis. HOW TO ARRIVE: The classic scenario = (1) African-American or Mediterranean male, (2) sudden hemolysis after exposure to an oxidant drug (primaquine, dapsone, co-trimoxazole, nitrofurantoin, antimalarials), (3) Heinz bodies (denatured Hb precipitates) and bite cells on smear, (4) DAT NEGATIVE (not immune-mediated). G6PD is the enzyme that protects RBCs from oxidative damage via the pentose phosphate pathway; its deficiency leads to oxidative hemolysis.

A 6-month-old infant (previously asymptomatic) develops pallor, jaundice, and irritability after his mother gives him some fava beans. Hb drops acutely. Peripheral smear shows Heinz bodies and schistocytes. The baby is male. DAT is negative. What is the diagnosis?	DIAGNOSIS: G6PD Deficiency — Favism (Fava Bean–Triggered Hemolysis). HOW TO ARRIVE: Favism is the classic trigger for G6PD deficiency in Mediterranean populations (also seen in Asians). Fava beans contain vicine and convicine, potent oxidants. Male infant + fava bean exposure + Heinz bodies + DAT negative = G6PD deficiency. The condition is X-linked recessive, so males are predominantly affected. The age of onset (after 6 months) is also a clue — before this, fetal Hb protects.

A 20-year-old man with known G6PD deficiency presents with hemolytic crisis during an episode of severe pneumonia. No drug exposure. Hb is 6 g/dL. Smear shows Heinz bodies. DAT is negative. What is the diagnosis?	DIAGNOSIS: G6PD Deficiency — Infection-Triggered Hemolytic Crisis. HOW TO ARRIVE: Infection (via oxidative stress from neutrophil respiratory burst) is a common trigger for hemolysis in G6PD deficiency, not just drugs. The triad of (1) known G6PD deficiency, (2) acute febrile illness, (3) Heinz bodies + DAT-negative hemolysis confirms this. Infections such as pneumonia, typhoid, and viral illness are recognized triggers.

A 3-year-old boy is referred for neonatal jaundice that required prolonged phototherapy. He now has mild chronic hemolytic anemia with occasional gallstones found on ultrasound. Family history is negative for hemolytic anemia. G6PD enzyme assay shows severely reduced activity. What is the diagnosis?	DIAGNOSIS: Chronic Non-Spherocytic Hemolytic Anemia due to G6PD Deficiency (Class I — Severe Variant). HOW TO ARRIVE: Most G6PD deficiency (Class II, III) is episodic. Class I is the rare severe form causing chronic hemolytic anemia even without triggers. Clues: male child, chronic hemolysis from infancy, neonatal jaundice requiring phototherapy, no family history (X-linked), and severely reduced G6PD enzyme assay. Gallstones in a young child always suggest chronic hemolysis.

A 35-year-old woman of Mediterranean origin presents with hemolytic anemia after starting a course of co-trimoxazole. Peripheral smear shows Heinz bodies. Haptoglobin is very low. During the recovery phase, reticulocytes are very high. G6PD enzyme assay done during the acute crisis is reported as NORMAL. What is the diagnosis and how do you explain the normal G6PD?	DIAGNOSIS: G6PD Deficiency — False-Normal Enzyme Assay During Acute Crisis. HOW TO ARRIVE: During an acute hemolytic crisis, the oldest (most G6PD-deficient) RBCs are destroyed, leaving behind young RBCs (reticulocytes) which have HIGHER G6PD activity — making the assay appear falsely normal. G6PD enzyme assay should be done 2–3 months after the crisis (during steady state) for accurate diagnosis. This is a frequently tested concept in NEET PG.

A 10-year-old child presents with mild jaundice and pallor since infancy. On examination, splenomegaly is noted. Hb is 9 g/dL. Peripheral smear shows SPHEROCYTES with increased MCHC (>36 g/dL). Osmotic fragility test is INCREASED. Family history: the father had a splenectomy for anemia in his 30s. What is the diagnosis?	DIAGNOSIS: Hereditary Spherocytosis (HS). HOW TO ARRIVE: The classic features are (1) spherocytes on smear + increased MCHC, (2) INCREASED osmotic fragility (spherocytes lyse more easily in hypotonic saline), (3) autosomal dominant inheritance (father affected), (4) splenomegaly from chronic extravascular hemolysis, (5) onset in childhood. The defective protein is spectrin, ankyrin, or band 3 — causing loss of RBC membrane surface area, converting them to spheres.

A 15-year-old boy with known hereditary spherocytosis presents with sudden worsening of anemia (Hb drops from 10 to 4 g/dL), fever, and high reticulocyte count of 0%. He is very ill. What is the diagnosis of this complication?	DIAGNOSIS: Aplastic Crisis in Hereditary Spherocytosis — caused by Parvovirus B19 infection. HOW TO ARRIVE: Aplastic crisis = sudden severe anemia + ABSENT reticulocytes (reticulocyte count of 0%) in a patient with chronic hemolytic anemia. Parvovirus B19 infects erythroid progenitors (which express P antigen), causing temporary cessation of erythropoiesis. In HS (with high baseline RBC turnover), even a temporary pause in production leads to life-threatening anemia. This is distinct from hemolytic crisis (where reticulocytes are HIGH).

An 8-year-old boy presents with episodic jaundice and anemia, often triggered by febrile illness. Hb 9 g/dL. Peripheral smear shows spherocytes. Osmotic fragility is increased. EMA (eosin-5-maleimide) binding test on flow cytometry shows REDUCED fluorescence. What is the diagnosis?	DIAGNOSIS: Hereditary Spherocytosis — Confirmed by EMA Binding Test. HOW TO ARRIVE: The EMA binding test is the BEST/GOLD STANDARD screening test for HS. EMA binds to band 3 (and related proteins) on the RBC surface. In HS, reduced band 3/ankyrin/spectrin → reduced EMA fluorescence on flow cytometry. Combined with spherocytes on smear and increased osmotic fragility, this confirms HS. The EMA test is preferred over osmotic fragility for its sensitivity and specificity.

A child with hereditary spherocytosis is scheduled for splenectomy. Post-splenectomy, peripheral smear shows Howell-Jolly bodies (nuclear remnants in RBCs). The hemolytic anemia is now compensated. What pre-operative vaccination is mandatory before splenectomy?	DIAGNOSIS: Post-Splenectomy Status in Hereditary Spherocytosis (this is a diagnostic identification card). HOW TO ARRIVE: Howell-Jolly bodies appear post-splenectomy because the spleen normally removes nuclear remnants from RBCs. Their presence on smear = functional or anatomical asplenia. In HS, splenectomy is curative (corrects anemia) but does NOT correct spherocytes — smear still shows spherocytes, but they are no longer destroyed. Pre-op vaccines: Pneumococcus, Meningococcus, H. influenzae type b (encapsulated organisms).

A 30-year-old man presents with recurrent episodes of dark-brown urine in the MORNING (hemoglobinuria), along with fatigue, abdominal pain, and recurrent thrombosis (portal vein thrombosis). CBC shows pancytopenia (low RBC, WBC, and platelets). Hemosiderinuria is detected on urine Prussian blue stain. Flow cytometry of blood cells shows ABSENT CD55 and CD59. What is the diagnosis?	DIAGNOSIS: Paroxysmal Nocturnal Hemoglobinuria (PNH). HOW TO ARRIVE: The classic triad of PNH is (1) Hemolytic anemia (intravascular — dark urine, especially morning), (2) Thrombosis (especially unusual sites: portal, hepatic, cerebral vein), (3) Cytopenias. The pathognomonic finding is ABSENT CD55 and CD59 on flow cytometry. These GPI-anchored complement regulatory proteins are absent due to a PIG-A gene mutation → uncontrolled complement lysis of RBCs. Morning hemoglobinuria = concentrated overnight urine amplifies complement activation.

A 25-year-old woman with PNH develops sudden severe abdominal pain with ascites. Ultrasound shows hepatic vein thrombosis (Budd-Chiari syndrome). Labs confirm she has PNH. What is the characteristic finding on flow cytometry that confirms PNH?	DIAGNOSIS: PNH with Budd-Chiari Syndrome. HOW TO ARRIVE: PNH is the MOST COMMON cause of Budd-Chiari syndrome in young patients (especially in India). Thrombosis occurs because complement activation leads to platelet activation and a prothrombotic state. Flow cytometry showing ABSENT/reduced CD55 and CD59 on RBCs, granulocytes, and monocytes is diagnostic. The PIG-A gene mutation (on chromosome Xp22.1) blocks GPI-anchor synthesis, depleting all GPI-linked proteins including CD55 (decay-accelerating factor) and CD59 (membrane inhibitor of reactive lysis).

A 35-year-old man presents with recurrent dark urine and anemia. Ham's (acid hemolysis) test is POSITIVE. Sugar water (sucrose lysis) test is also POSITIVE. He has pancytopenia. What is the diagnosis?	DIAGNOSIS: Paroxysmal Nocturnal Hemoglobinuria (PNH). HOW TO ARRIVE: Ham's test (acidified serum lysis test) = positive in PNH. The acidic environment activates the alternate complement pathway, which lyses PNH RBCs (lacking CD55 and CD59). Sugar water test = also positive in PNH (sucrose lowers ionic strength → complement activation → lysis of PNH cells). These older tests have been replaced by flow cytometry (CD55/CD59) which is now the gold standard, but Ham's test is still heavily tested in NEET PG MCQs.

A patient with known aplastic anemia on immunosuppressive therapy develops a new clone of cells with PIG-A mutation. Peripheral blood flow cytometry shows a population of RBCs lacking CD59. The patient develops hemolysis and thrombocytopenia. What is the diagnosis?	DIAGNOSIS: PNH Evolving from Aplastic Anemia. HOW TO ARRIVE: PNH and aplastic anemia share a pathophysiological link — both involve destruction of hematopoietic stem cells (by autoimmune T-cells). PNH clones can emerge in aplastic anemia (and vice versa). A new CD59-negative population on flow cytometry in a patient with aplastic anemia = PNH transformation. This is why all aplastic anemia patients need periodic flow cytometry monitoring. The PIG-A mutation gives a survival advantage to the clone under immune attack.

A 40-year-old man complains of difficulty swallowing (dysphagia), erectile dysfunction, and chronic fatigue. He has recurrent morning dark urine. Hb is 8 g/dL with elevated LDH. Flow cytometry shows absent CD55 and CD59 on blood cells. What is the diagnosis?	DIAGNOSIS: PNH with Smooth Muscle Dystonia. HOW TO ARRIVE: Nitric oxide (NO) scavenging by free hemoglobin (released during intravascular hemolysis in PNH) causes smooth muscle dystonia → dysphagia, abdominal cramps, and erectile dysfunction. This is a unique and highly testable feature of PNH. The combination of morning hemoglobinuria + esophageal spasm/dysphagia + erectile dysfunction + absent CD55/CD59 = classic PNH presentation. LDH is the best marker for intravascular hemolysis.

A 2-year-old child from West Africa presents with dactylitis (painful swelling of hands and feet), fever, and irritability. Hb is 7 g/dL. Peripheral smear shows sickle-shaped red blood cells. Hb electrophoresis shows HbS 90%, HbA2 2%, HbF 8%, HbA 0%. What is the diagnosis?	DIAGNOSIS: Sickle Cell Disease (HbSS — Sickle Cell Anemia). HOW TO ARRIVE: (1) African origin, (2) dactylitis is the FIRST clinical manifestation in infants (2-year-old), (3) peripheral smear with sickled RBCs, (4) Hb electrophoresis: NO HbA (= 0%) with predominantly HbS (~90%) + small HbF = homozygous HbSS (sickle cell anemia). HbA2 is normal (2%). Dactylitis results from vasoocclusion of small bones of hands/feet by sickled cells — classic pediatric presentation.

A 20-year-old man presents with severe bone pain (pain crisis) involving the back and long bones, following a viral upper respiratory infection. He is known to have sickle cell disease. X-ray shows no acute bone abnormalities. Hb is 7 g/dL. Sickling test (sickle solubility test) is POSITIVE. What is the diagnosis?	DIAGNOSIS: Sickle Cell Disease — Vaso-Occlusive (Pain) Crisis. HOW TO ARRIVE: The most common complication of sickle cell disease. Triggers: infection, dehydration, hypoxia, cold, acidosis — all worsen sickling. HbS polymerizes under low oxygen conditions → rigid sickled cells occlude microvasculature → ischemic bone pain (the most common crisis type). The sickling test (sodium metabisulfite or sodium dithionite) is POSITIVE for HbS. No X-ray changes acutely differentiates vaso-occlusive crisis from osteomyelitis.

A 15-year-old girl with sickle cell disease presents with sudden onset left upper quadrant pain, rapid enlargement of the spleen, and a sharp drop in Hb from baseline 8 g/dL to 3 g/dL with no reticulocytopenia (reticulocytes are HIGH). What is this acute complication?	DIAGNOSIS: Sickle Cell Disease — Acute Splenic Sequestration Crisis. HOW TO ARRIVE: Acute sequestration = sudden trapping of a large volume of blood in the spleen → rapid splenic enlargement, hypovolemic shock, and sharp Hb drop with HIGH reticulocyte count (bone marrow is still active). Occurs in young children with sickle cell disease (before autosplenectomy occurs). Contrast with aplastic crisis (Hb drops + reticulocytes are ZERO). This is a medical emergency requiring urgent blood transfusion.

A 25-year-old man with sickle cell disease is found to have a hemoglobin of 5.5 g/dL (baseline 7 g/dL), with a reticulocyte count of 0.2%. He has fever and mild rash. No pain crisis. What is the diagnosis?	DIAGNOSIS: Sickle Cell Disease — Aplastic Crisis due to Parvovirus B19. HOW TO ARRIVE: Parvovirus B19 infects erythroid progenitors → temporary cessation of RBC production → reticulocyte count drops to NEAR-ZERO. In sickle cell disease with its short RBC lifespan (~20 days), even a brief production halt causes life-threatening anemia. Key differentiator from sequestration crisis: reticulocytes are LOW/ABSENT (not high). Rash (slapped-cheek pattern) may be present. Both HS and SCD are tested with this aplastic crisis scenario.

A newborn in India is screened for hemoglobinopathy. Hb electrophoresis shows HbA 55%, HbS 40%, HbA2 4%. The parents ask about the child's clinical status. What is the diagnosis?	DIAGNOSIS: Sickle Cell Trait (HbAS — Heterozygous Carrier). HOW TO ARRIVE: Hb electrophoresis: HbA >HbS with elevated HbA2. HbA ~55–60%, HbS ~35–45% = heterozygous carrier (sickle cell TRAIT), NOT disease. Sickle cell trait is generally BENIGN — no chronic hemolysis, normal life expectancy. HbA2 may be slightly elevated. Compared to HbSS (no HbA, predominantly HbS). Sickle cell trait does NOT cause vaso-occlusive crises or severe anemia — a common NEET PG trap.

A 3-year-old child born to Mediterranean parents presents with severe anemia (Hb 4 g/dL), hepatosplenomegaly, frontal bossing, and "hair-on-end" appearance on skull X-ray. Peripheral smear shows target cells, teardrop cells, and nucleated RBCs. Hb electrophoresis shows HbA 0%, HbF 95%, HbA2 5%. What is the diagnosis?	DIAGNOSIS: Beta-Thalassemia Major (Cooley's Anemia). HOW TO ARRIVE: (1) Mediterranean/Asian child, (2) severe transfusion-dependent anemia from infancy, (3) massive hepatosplenomegaly (extramedullary hematopoiesis), (4) frontal bossing + "hair-on-end" skull X-ray (medullary expansion of bone marrow), (5) Hb electrophoresis: HbA = 0% (no beta chains synthesized) + HbF = 95% (compensatory fetal Hb) + elevated HbA2. Target cells and nucleated RBCs on smear. This is beta-zero thalassemia (complete absence of beta-globin chains).

A 20-year-old Asian man presents with mild anemia (Hb 10 g/dL), mild splenomegaly, and occasional jaundice. MCV is 60 fL (microcytic). Peripheral smear shows target cells and hypochromic microcytic RBCs. Hb electrophoresis shows HbA 92%, HbA2 5.5%, HbF 2%. Serum ferritin is NORMAL. What is the diagnosis?	DIAGNOSIS: Beta-Thalassemia Minor (Trait/Carrier). HOW TO ARRIVE: The HALLMARK is elevated HbA2 >3.5% (typically 4–7%) on Hb electrophoresis — the most reliable diagnostic test. Mild microcytic hypochromic anemia with NORMAL serum ferritin (differentiates from iron deficiency anemia where ferritin is low). Target cells on smear. Clinically mild — patients are usually asymptomatic or have only mild anemia. Do NOT treat with iron (ferritin is normal). This is the most commonly tested thalassemia scenario in NEET PG.

A couple comes for premarital counseling. Both partners are found to have elevated HbA2 (5%) with microcytic anemia and normal ferritin. They are concerned about offspring. What is the diagnosis of each partner, and what is the risk for their offspring?	DIAGNOSIS: Both parents have Beta-Thalassemia Trait (Beta-Thalassemia Minor). HOW TO ARRIVE: Elevated HbA2 >3.5% with microcytic anemia = beta-thalassemia trait in each parent. When both parents carry the beta-thalassemia trait: 25% chance of normal child, 50% chance of trait (like parents), 25% chance of beta-thalassemia MAJOR (severely affected). This is a classic genetics counseling scenario. The Hb electrophoresis finding of elevated HbA2 is the SINGLE MOST IMPORTANT test to diagnose beta-thalassemia minor.

A 6-month-old infant from Southeast Asia presents with severe hydrops fetalis and is stillborn. The placenta is enlarged. Hb electrophoresis of cord blood shows predominantly Hb Barts (gamma-4 tetramers) with no HbA, no HbF. What is the diagnosis?	DIAGNOSIS: Alpha-Thalassemia Major (Hb Barts Hydrops Fetalis — deletion of all 4 alpha-globin genes). HOW TO ARRIVE: Deletion of all four alpha-globin genes → no alpha chains → only gamma-4 tetramers (Hb Bart's) form → extremely high oxygen affinity (useless for tissue delivery) → fatal hydrops fetalis. Hb Barts on electrophoresis is diagnostic. Southeast Asian ancestry (high prevalence of alpha gene deletions). Death in utero or shortly after birth. Hb Barts = 4 deletions; HbH disease = 3 deletions; Alpha-thal minor = 2 deletions; Silent carrier = 1 deletion.

A patient with sickle cell disease shows on Hb electrophoresis: HbS 70%, HbC 25%, HbF 5%, HbA 0%. He has milder disease than classic sickle cell anemia. What is the diagnosis?	DIAGNOSIS: Hemoglobin SC Disease (HbSC). HOW TO ARRIVE: HbSC = heterozygous for HbS and HbC (both abnormal beta-globin alleles, no normal HbA). Milder course than HbSS but still causes sickle-related complications, notably proliferative retinopathy and avascular necrosis more commonly than HbSS. Hb electrophoresis: HbS ~50%, HbC ~50% (or HbS 70%/HbC 25% with some HbF) — key point is NO HbA. Target cells are characteristic on smear. Higher Hb than HbSS (~10–11 g/dL) due to relative polycythemia.

A 5-year-old child presents with easy bruising and prolonged bleeding after minor cuts. Platelet count is 15,000/µL (low). Bleeding time is prolonged. PT and aPTT are NORMAL. Peripheral smear shows GIANT platelets (thrombocytes appearing as large as RBCs). No splenomegaly. What is the diagnosis?	DIAGNOSIS: Bernard-Soulier Syndrome (BSS). HOW TO ARRIVE: The classic triad is (1) THROMBOCYTOPENIA with GIANT platelets on smear, (2) PROLONGED bleeding time (platelet dysfunction), (3) NORMAL PT and aPTT (coagulation cascade is intact). BSS is due to deficiency of GPIb-IX-V complex on platelet surface → cannot bind von Willebrand factor (vWF) → defective platelet adhesion. The giant platelets (macro-thrombocytes) are the morphological hallmark. Autosomal recessive. No splenomegaly (differentiates from ITP where platelets are small/normal sized).

A 10-year-old boy has mucocutaneous bleeding since childhood. Platelet count is NORMAL (250,000/µL). Bleeding time is markedly prolonged. Clot retraction is ABSENT. Platelet aggregation studies show: no aggregation with ADP, collagen, thrombin, or epinephrine, but NORMAL aggregation with RISTOCETIN. What is the diagnosis?	DIAGNOSIS: Glanzmann Thrombasthenia (GT). HOW TO ARRIVE: The KEY pattern is: (1) Normal platelet count, (2) Prolonged bleeding time, (3) Absent clot retraction, (4) No platelet aggregation with ALL agonists EXCEPT ristocetin (which tests GPIb, not GPIIb/IIIa). GT = deficiency of GPIIb/IIIa (integrin αIIbβ3) → cannot bind fibrinogen → no platelet-to-platelet aggregation. Ristocetin induces vWF-GPIb binding (doesn't need GPIIb/IIIa), so it is NORMAL in GT. Autosomal recessive, common in Gujarati/Iraqi Jewish populations in India.

A 12-year-old girl with recurrent epistaxis and gum bleeding has normal platelet count and normal PT/aPTT. Peripheral smear shows normal platelet morphology and count. Clot retraction test is ABNORMAL (absent). Platelet aggregation: absent with ADP and collagen, present with ristocetin. What is the diagnosis?	DIAGNOSIS: Glanzmann Thrombasthenia. HOW TO ARRIVE: Absent clot retraction is almost PATHOGNOMONIC of Glanzmann thrombasthenia. Normal count + normal morphology + prolonged bleeding time + absent clot retraction + absent aggregation (except with ristocetin) = GT. Clot retraction requires platelet GPIIb/IIIa to bind fibrin during clot formation. Its absence directly reflects the GPIIb/IIIa deficiency. Bernard-Soulier (BSS) has giant platelets and thrombocytopenia — key differentiator.

A 6-year-old child from a consanguineous family presents with recurrent heavy bleeding from tooth extraction. Platelet count and morphology are normal. PT and aPTT are normal. Bleeding time is very prolonged. Platelet aggregation is absent with ADP, collagen, epinephrine, and thrombin, but normal with ristocetin. Dense granule secretion is absent. What is the diagnosis?	DIAGNOSIS: Glanzmann Thrombasthenia — Autosomal Recessive. HOW TO ARRIVE: Consanguinity (autosomal recessive condition), bleeding symptoms, normal count, absent aggregation with all agonists except ristocetin, absent clot retraction = Glanzmann thrombasthenia. The normal ristocetin response distinguishes GT from BSS (where ristocetin response is also ABNORMAL because GPIb is deficient in BSS). GT type I: <5% GPIIb/IIIa; Type II: 10–20%; Variant: >50% but dysfunctional.

A 16-year-old girl presents with menorrhagia and easy bruising. Platelet count is normal. vWF antigen and activity are normal. Ristocetin cofactor assay is normal. Platelet aggregation is absent with ADP and collagen. Clot retraction is absent. What is the diagnosis?	DIAGNOSIS: Glanzmann Thrombasthenia — presenting as Menorrhagia in an Adolescent Girl. HOW TO ARRIVE: GT is a common cause of menorrhagia in adolescent girls with inherited platelet disorders (along with vWD). The differentiator from vWD: (1) vWF studies are NORMAL in GT (vWD has low vWF), (2) ristocetin cofactor is normal, (3) absent clot retraction (vWD has present clot retraction). Normal vWF + absent aggregation (ADP/collagen) + absent clot retraction = GT. Always test platelet aggregation in adolescent girls with unexplained menorrhagia.

An 8-year-old has mucocutaneous bleeding. Platelet count is low (80,000/µL) with giant platelets. Ristocetin-induced platelet aggregation (RIPA) is ABSENT. PT/aPTT are normal. What is the diagnosis?	DIAGNOSIS: Bernard-Soulier Syndrome. HOW TO ARRIVE: BSS = Low platelet count + GIANT platelets + ABSENT RIPA (ristocetin response). Absent RIPA is because ristocetin acts through the GPIb receptor — which is deficient in BSS. This is the KEY differentiator from Glanzmann: In GT, RIPA is NORMAL (GPIb intact). In BSS, RIPA is ABSENT (GPIb deficient). Additional features: autosomal recessive, prolonged bleeding time, normal PT/aPTT, and absence of aggregation with ristocetin (but often normal aggregation with ADP, collagen, and epinephrine in BSS).

A 60-year-old man on unfractionated heparin (UFH) for DVT is noted to have a platelet count drop from 320,000/µL to 90,000/µL on day 8 of treatment. He develops a new DVT in the contralateral leg despite therapeutic anticoagulation. 4T score is calculated as HIGH probability. What is the diagnosis?	DIAGNOSIS: Heparin-Induced Thrombocytopenia Type II (HIT). HOW TO ARRIVE: The classic HIT scenario: (1) Platelet count falls 50% or more, typically on day 5–14 of heparin (day 8 here), (2) THROMBOSIS despite anticoagulation (paradoxical — platelet count low but thrombosis occurs), (3) 4T score (Thrombocytopenia, Timing, Thrombosis, oTher causes excluded) = high probability. HIT is caused by IgG antibodies against PF4-heparin complexes → platelet activation → thrombosis. Treatment: STOP ALL HEPARIN (including flushes) and switch to non-heparin anticoagulant (argatroban, fondaparinux, bivalirudin).

A patient on heparin develops thrombocytopenia on day 2. Platelet count drops mildly (230,000 to 180,000/µL). No thrombosis. What is the diagnosis?	DIAGNOSIS: Heparin-Induced Thrombocytopenia Type I (HIT Type I — Non-immune). HOW TO ARRIVE: HIT Type I = mild, transient, early (days 1–4) platelet drop due to direct heparin-platelet interaction (NOT immune-mediated). Platelet count usually stays above 100,000/µL and recovers spontaneously even if heparin is continued. NO antibodies against PF4-heparin. NO thrombosis. Contrast with HIT Type II: day 5–14 onset, >50% platelet drop, IMMUNE-mediated (PF4-heparin antibodies), associated with THROMBOSIS, and requires stopping heparin. HIT Type I is clinically benign and does NOT require stopping heparin.

A patient who received cardiac surgery 5 days ago and received large amounts of heparin intraoperatively now presents with platelet count of 60,000/µL (was 280,000 pre-op) on day 5. Doppler ultrasound shows a new upper extremity deep vein thrombosis. Anti-PF4/heparin antibody (ELISA) is POSITIVE. Serotonin release assay (SRA) is also POSITIVE. What is the diagnosis?	DIAGNOSIS: Heparin-Induced Thrombocytopenia Type II (HIT) — Post-Cardiac Surgery. HOW TO ARRIVE: Post-cardiac surgery patients receive large heparin loads → increased risk of HIT. Day 5 onset of >50% platelet drop + new thrombosis = HIT until proven otherwise. Diagnosis confirmed by: (1) PF4/heparin antibody ELISA (highly sensitive screening test), (2) Serotonin Release Assay (SRA) = gold standard functional assay (most specific). Management: stop ALL heparin, start non-heparin anticoagulant. Platelet transfusions are CONTRAINDICATED in HIT (fuel for further thrombosis).

A patient on LMWH (low molecular weight heparin) for pulmonary embolism develops sudden platelet count drop from 250,000 to 100,000 on day 7. Anti-PF4/heparin ELISA is positive. What is the diagnosis and can LMWH cause this?	DIAGNOSIS: HIT Type II — caused by LMWH. HOW TO ARRIVE: LMWH can cause HIT, but the risk is LOWER than with UFH (~0.1–1% vs. ~1–5% for UFH). Fondaparinux has the lowest risk. The pathophysiology is the same — IgG antibodies against PF4-heparin complexes. Day 7 onset + >50% platelet drop + positive ELISA in a patient on LMWH = HIT Type II. Treatment: stop LMWH, switch to non-heparin anticoagulant. Do NOT switch from UFH to LMWH in HIT (cross-reactivity).

A critically ill patient develops severe thrombocytopenia (platelet count 20,000/µL) while in the ICU on continuous heparin infusion. The 4T score is 6/8 (high probability). How is HIT definitively confirmed, and what is the treatment?	DIAGNOSIS: HIT Type II — High Pre-test Probability (Confirmed by Functional Assay). HOW TO ARRIVE: 4T score >5 = high probability of HIT. Diagnostic steps: (1) ELISA for PF4-heparin antibody = screening (sensitive); (2) Serotonin Release Assay (SRA) = gold standard confirmatory test. Treatment: (1) Stop ALL forms of heparin (including heparin flushes, heparin-coated catheters), (2) Start non-heparin anticoagulant: argatroban (direct thrombin inhibitor), bivalirudin, or fondaparinux, (3) Do NOT give platelet transfusions, (4) Do NOT start warfarin until platelets recover (risk of venous limb gangrene).

A 25-year-old woman presents with easy bruising and heavy menstrual bleeding for 3 months. Platelet count is 18,000/µL. Peripheral smear shows only low platelet numbers, but platelets appear large. WBC and RBC are NORMAL. PT and aPTT are NORMAL. Bone marrow biopsy shows increased megakaryocytes. No splenomegaly. Antinuclear antibody (ANA) is negative. What is the diagnosis?	DIAGNOSIS: Primary Immune Thrombocytopenic Purpura (ITP) — Adult Type. HOW TO ARRIVE: Classic adult ITP: (1) isolated thrombocytopenia (normal WBC, RBC), (2) large platelets on smear (young, newly released), (3) NORMAL PT/aPTT (platelet problem, not coagulation), (4) bone marrow: increased megakaryocytes (destruction at periphery, compensatory production), (5) no splenomegaly, (6) exclusion of secondary causes (ANA negative, no drugs, no infections). Pathophysiology: IgG autoantibodies against GPIIb/IIIa → macrophage-mediated platelet destruction in spleen.

A 6-year-old child develops sudden onset petechiae and purpura all over the body 2 weeks after a viral upper respiratory tract infection. Platelet count is 10,000/µL. PT and aPTT are normal. Bone marrow shows increased megakaryocytes. What is the diagnosis and expected outcome?	DIAGNOSIS: Acute ITP (Childhood ITP) — Post-Infectious. HOW TO ARRIVE: Childhood ITP (acute form): (1) sudden onset of thrombocytopenia 1–3 weeks after a viral infection (molecular mimicry — antibodies against viral antigens cross-react with platelets), (2) previously healthy child, (3) petechiae and purpura (mucocutaneous bleeding), (4) isolated thrombocytopenia with normal CBC otherwise, (5) increased megakaryocytes on bone marrow. Prognosis: 80–90% of children with acute ITP recover spontaneously within 6 months without treatment. This distinguishes it from adult ITP which tends to be chronic.

A 35-year-old HIV-positive man presents with easy bruising and gum bleeding. Platelet count is 30,000/µL. His CD4 count is 350/µL. PT and aPTT are normal. Bone marrow shows adequate megakaryocytes. What is the diagnosis?	DIAGNOSIS: ITP Secondary to HIV Infection. HOW TO ARRIVE: HIV is a common cause of SECONDARY ITP. HIV directly affects platelets (binding to GPIIb/IIIa) and causes immune-mediated platelet destruction. Isolated thrombocytopenia in an HIV-positive patient with adequate megakaryocytes on bone marrow = HIV-associated ITP. CD4 count is usually preserved in early HIV-ITP (350/µL). Treatment of the underlying HIV with antiretrovirals often improves platelet count. Always test for HIV in otherwise unexplained thrombocytopenia in adults (a NEET PG exam favorite).

A woman diagnosed with ITP 2 years ago has failed steroid therapy and splenectomy. Platelet count remains at 25,000/µL. She has no bleeding currently. What is the next step in management? (Identify the diagnosis first.)	DIAGNOSIS: Refractory/Chronic ITP — Persistent Thrombocytopenia after Splenectomy. HOW TO ARRIVE: ITP is classified as: (1) Newly diagnosed (<3 months), (2) Persistent (3–12 months), (3) Chronic (>12 months). Refractory ITP = no response to both steroids AND splenectomy. Treatment options for refractory ITP: Thrombopoietin receptor agonists (TPO-RAs) = eltrombopag (oral) or romiplostim (subcutaneous injection), rituximab (anti-CD20). Splenectomy is the procedure of choice for steroid-refractory ITP. Knowing this hierarchy (steroids → splenectomy → TPO-RAs) is critical for NEET PG.

A 28-year-old pregnant woman in the third trimester is found to have a platelet count of 85,000/µL on routine CBC. She has no bleeding symptoms. No prior history of thrombocytopenia. All other CBC parameters are normal. What is the diagnosis?	DIAGNOSIS: Gestational Thrombocytopenia (NOT ITP). HOW TO ARRIVE: Gestational thrombocytopenia is the most common cause of thrombocytopenia in pregnancy (75% of cases). Key differentiators from ITP: (1) occurs only in late 2nd or 3rd trimester, (2) mild thrombocytopenia (platelets rarely <70,000/µL), (3) no prior history of thrombocytopenia, (4) no bleeding symptoms, (5) resolves spontaneously after delivery. ITP in pregnancy is more severe and can occur in any trimester with prior history. This distinction is a common NEET PG question in the obstetrics section.

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