Pallor

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Pallor

Definition

Pallor is an abnormal paleness of the skin, mucous membranes, or conjunctivae resulting from reduced blood flow to the periphery, reduced hemoglobin content, or reduced red cell mass.

Causes of Pallor

Pallor has two broad mechanisms:

1. Reduced Red Cell Mass (Anemia)

The most common cause. When hemoglobin falls, the blood carries less oxygen-bound pigment, making tissues appear pale.

Category	Examples
Blood loss (hemorrhage)	GI bleeding, trauma, menorrhagia
Reduced RBC production	Iron deficiency, B12/folate deficiency, aplastic anemia, anemia of chronic disease
Increased RBC destruction	Hemolytic anemias (G6PD deficiency, thalassemia, autoimmune hemolysis)
Bone marrow failure	Aplastic anemia, leukemia, myelodysplasia

2. Peripheral Vasoconstriction (Without Anemia)

Blood is shunted away from the skin to vital organs. This produces pallor even with normal hemoglobin.

Shock (hypovolemic, cardiogenic) - tachycardia, peripheral vasoconstriction, cool-pale skin is the classic "shocky" presentation. Notably, septic shock may initially cause warm, flushed skin before vasoconstriction sets in.
Exposure to cold - reflex vasoconstriction
Vasovagal syncope / vasomotor instability
Nicotinic effects of cholinesterase inhibitor toxicity (organophosphate poisoning) - mydriasis, pallor, tachycardia, hypertension
Autonomic instability (e.g., neuroleptic malignant syndrome) - pallor, diaphoresis, labile BP

Sites of Assessment and Clinical Significance

The site of pallor assessment matters considerably:

Site	Clinical Significance
Conjunctival mucosa	Most specific; pallor here (anterior rim same color as posterior) has LR+ of 16.7 for anemia; generally suggests Hb < 9 g/dL
Palmar creases	When creases fail to become prominent on palm extension, suggests Hb ≤ 7-8 g/dL; LR+ 7.9
Facial, nail beds	Less useful - LR+ < 5
Tongue, oral mucosa, nails	Used in clinical practice; correlate findings together

Key points from Symptom to Diagnosis, 4th Ed.:

Absence of pallor does not rule out anemia

No single physical sign rules out anemia

Overall sensitivity and specificity of physical exam for anemia is ~70%

Order a CBC if symptoms suggest anemia, even without physical signs, or if conjunctival rim or palmar crease pallor is observed

Pallor in Specific Conditions

Iron deficiency anemia: Pallor + pica (eating ice) + restless leg syndrome; most common cause of anemia overall
B12/folate deficiency: Megaloblastic anemia; patients may present at very low Hb because of slow onset with cardiovascular accommodation
Aplastic anemia: Pallor + fatigue + petechiae + infections (pancytopenia triad)
Thalassemia (Mediterranean anemia): Diffuse pallor and cyanosis of oral mucosa
Chronic lead poisoning: Characteristic facial pallor (especially perioral) + punctate basophilia + lead line on gums + colic
Shock: Cool, pale skin with tachycardia - peripheral vasoconstriction preserves perfusion to brain and heart

Associated Symptoms and Physical Findings in Anemia

Accompanying features to look for:

Fatigue (common, nonspecific)
Palpitations / tachycardia - increased cardiac output to maintain O2 delivery
Systolic ejection murmur - hyperdynamic circulation
Dyspnea on exertion
Peripheral edema - combination of high-output cardiac state and reduced oncotic pressure
Jaundice - suggests hemolysis
Retinal hemorrhages - seen on fundoscopy in severe anemia (rare)
Splenomegaly - hemolytic anemias
Pica, restless legs - iron deficiency specifically

All vascular and cardiac manifestations resolve with correction of the anemia.

IMCI / Pediatric Assessment (WHO Approach)

In children, the WHO IMCI protocol uses palmar pallor to classify anemia:

Severe palmar pallor - severe anemia; assess for sickle cell if prevalent in the region
Some palmar pallor - some anemia

Diagnostic Approach

Confirm with CBC (hemoglobin, hematocrit, MCV, reticulocyte count)
MCV guides the differential:
- Microcytic (MCV < 80): iron deficiency, thalassemia, anemia of inflammation
- Normocytic: aplastic anemia, hemolysis, acute blood loss
- Macrocytic (MCV > 100): B12 or folate deficiency
History: blood loss, diet (vegetarian/vegan), medications, pregnancies, family history
Examine: jaundice, organomegaly, petechiae, lymphadenopathy, neurologic signs
Consider: iron studies, B12/folate, reticulocyte count, peripheral smear, Coombs test

Sources: Goldman-Cecil Medicine, p. 1670; Symptom to Diagnosis 4th Ed., p. 121; Robbins Basic Pathology; Park's Preventive Medicine; Tintinalli's Emergency Medicine

Pallor

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