Spherocytosis, Hereditary

Disorder of RBC membrane, leading to chronic hemolytic anemia

Autosomal dominant disease of variable severity

Membrane defect is in spectrin or actin, RBC skeleton proteins, resulting in decreased surface–volume ratio and a spherical RBC shape, which is less deformable

Hemolysis occurs because of trapping of RBCs within the spleen and their premature removal by splenic macrophages

Often diagnosed in childhood, but milder cases discovered incidentally late in life. Family history often positive

Anemia may or may not be present because bone marrow may be able to compensate for shortened RBC survival

Severe anemia (aplastic crisis) may occur with folic acid deficiency or infection

Chronic hemolysis causes

• Jaundice

• Pigment (calcium bilirubinate) gallstones, leading to attacks of cholecystitis

• Medial malleolar skin ulcers

Palpable spleen

Hyperchromic red blood cells (elevated mean corpuscular hemoglobin concentration [MCHC])

Anemia of variable severity; hematocrit may be normal

Increased MCHC, often > 36 g/dL

Reticulocytosis present

Peripheral blood smear shows small percentage of spherocytes, small cells that have lost their central pallor

Indirect bilirubin often increased

Coombs test negative

Increased osmotic fragility (abnormally vulnerable to swelling induced by hypotonic media) can be demonstrated by ektacytometry

EMA (eosin-5 maleimide) binding by flow cytometry is another diagnostic tool

Folic acid, 1 mg orally once daily

Splenectomy

• Eliminates site of hemolysis

• May not be necessary in mild cases discovered late in adult life