Hereditary Spherocytosis.

Autosomal dominant / Autosomal recessive (25% more severe) pattern of inheritance

Spherodial RBCs – which makes RBC less deformable and more vulnerable to splenic destruction.

Intrinsic defect in the RBC membrane.

Normally the biconcave shape of RBCs is function of RBC membrane proteins, specially spectrin and ankyrin, this proteins forms a meashlike network in intracellular face of membrane, this stabilize the membranes and is responsible of normal shape, strength and flexibility of RBC.

Mutations in this proteins leads to loosening of the membrane fragments as they are not stable, so the biconcave shape is disturbed, there by the surface area decreases, but the volume is not lost, so to maintain the ratio of surface area to volume, the RBC takes shape of sphere.

The spleen plays a major role in the destruction of spherocytes.

Cords of billroth -------splenic sinusoids.

The abnormal RBCs are sequestered and eventually destroyed by macrophages, which are plentiful in the splenic cords.

MORPHOLOGY

Microscopic - On smears, the RBCs lack the central zone of pallor because of their spheroidal shape. Increased erythropoiesis in the marrow is stimulated.

Peripheral smear shows – reticulocytosis.

Gross - Splenomegaly.