Which feature best distinguishes hereditary spherocytosis from hereditary elliptocytosis?

Distinguishing Hereditary Spherocytosis from Hereditary Elliptocytosis

Key Morphological and Functional Differences

Osmotic fragility testing is the gold standard discriminator. Hereditary spherocytosis RBCs lyse at higher saline concentrations (increased fragility) because their spherical shape with reduced surface-area-to-volume ratio cannot accommodate water influx. Hereditary elliptocytes remain intact in the same conditions due to their elongated shape and normal osmotic tolerance.

Incubated osmotic fragility (RBCs incubated at 37°C for 24 hours before testing) is even more discriminatory — spherocytes show marked increase in fragility, while elliptocytes remain normal. This test is rarely done in routine practice but is a classic NEET PG question stem.

Hereditary elliptocytosis patients are often asymptomatic and discovered incidentally on blood smear. Hereditary spherocytosis typically presents with jaundice, anemia, and splenomegaly requiring intervention.

Robbins 10e Ch 13