Stomatocytosis (red blood cells with a transverse slit or stoma across the center) and hypophosphatemia cause red blood cell membrane abnormalities that can result in hemolytic anemia.
(See also Overview of Hemolytic Anemia.)
Stomatocytosis
Stomatocytosis is a rare condition of red blood cells (RBCs) in which a mouthlike or slitlike pattern replaces the normal central zone of pallor. Stomatocytosis may be
Congenital
Acquired
Both congenital and acquired stomatocytosis may be asymptomatic or cause hemolysis. Symptoms, if present, result mainly from the anemia.
Congenital stomatocytosis, which shows autosomal dominant inheritance, is rare. It can cause a severe hemolytic anemia that manifests very early in life. The RBC membrane is hyperpermeable to monovalent cations (sodium and potassium); movement of divalent cations and anions is normal. Splenectomy may ameliorate anemia in severe cases, but careful consideration should be given to the increase in thromboembolic events that follows splenectomy (1) and splenectomy's less clear therapeutic benefit.
Acquired stomatocytosis with hemolytic anemia occurs primarily after excessive alcohol ingestion. Stomatocytes in the peripheral blood and hemolysis disappear within 2 weeks of alcohol withdrawal.
Anemia caused by hypophosphatemia
Red blood cell pliability varies according to intracellular adenosine triphosphate (ATP) levels. Because the serum phosphate concentration affects RBC ATP levels, a low serum phosphate level (< 0.5 mg/dL [< 0.16 mmol/L]) depletes ATP levels in RBCs. The complex metabolic sequelae of hypophosphatemia also include 2,3-diphosphoglyceric acid depletion, a shift to the left in the oxygen dissociation curve, decreased glucose utilization, and increased lactate production. The resultant rigid, nonyielding RBCs are susceptible to injury in the capillary circulatory bed, leading to hemolysis and small, sphere-shaped RBCs (spherocytosis).
Severe hypophosphatemia may occur in
Refeeding after starvation
The recovery (diuretic) phase after severe burns
Hyperalimentation
Severe respiratory alkalosis
Patients with uremia receiving dialysis who are taking antacids
Phosphate supplements prevent or reverse the anemia and are considered for patients at risk of or who have hypophosphatemia.
Reference
1. Stewart GW, Amess JA, Eber SW, et al. Thrombo-embolic disease after splenectomy for hereditary stomatocytosis. Br J Haematol 1996;93(2):303-310. doi:10.1046/j.1365-2141.1996.4881033.x
