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Series of inherited forms of hemolytic anemia caused by alterations in the red cell membrane, resulting in leakage of sodium and potassium. After resaturation of normal permeability, red cell membrane rigidity, morphology, water content, and cell cation return to normal. Low potassium is dominant to high potassium.

Cryohydrocytosis; Overhydrated Hereditary Stomatocytosis.

Unknown. Approximately 1:10,000 kindreds in France and the United Kingdom have hereditary xerocytosis. Familial pseudohyperkalemia does not seem to occur in the United States.

Autosomal dominant. Mutation located on chromosome 16, but the gene is not yet identified. Except for hereditary xerocytosis, the red blood cell membrane of stomatocytoses is defective for the stomatin protein (or “erythrocyte membrane protein 7.2b”).

The red blood cells have a membrane abnormality with increased permeability to cations, with a greater efflux of potassium than sodium. Consequently, these red cells lose potassium in excess of the sodium gained, with a decrease in total cation content.

Laboratory findings include hemoglobinuria, reticulocytosis, increased red cell hemolysis by shear stress, increased mean corpuscular volume, and increased mean corpuscular hemoglobin concentration. The visual aspect of red blood cells varies depending on the variant: very stomatocytic for the rather common overhydrated hereditary stomatocytosis, xerocytic for the rarer dehydrated hereditary stomatocytosis, and no anemia in familial pseudohyperkalemia.

Patients generally have few symptoms but may have exercise-induced episodes of fatigue, associated with jaundice, pallor, or darkened urine. Splenomegaly and cholelithiasis may occur. Hemoglobin levels are often normal or near-normal, despite clinical and laboratory evidence of mild-to-moderate hemolysis (except for familial pseudohyperkalemia). Blood transfusions are generally not required, and the benefit of splenectomy is slight. Furthermore, if the spleen is removed, problems with excessive blood clotting may arise later in life. Iron overload may develop later in life.

Check hemoglobin level and reticulocyte count.

Potential reduction in oxygen delivery because of decreased levels of 2,3-diphosphoglycerate.

No known specific implications for this condition.

Hereditary Spherocytosis: Genetically transmitted hemolytic anemia as a result of mutations in the spectrin gene in people of circum-Mediterranean descent; autosomal dominant and recessive forms are described.

Hereditary Pyropoikilocytosis: Autosomal dominant hemolytic medical condition in which erythrocytes have a bizarre morphology similar to that seen in thermal burns. It is probably the result of coinheritance of a mutation impairing spectrin association (and causing hereditary elliptocytosis) and a second mutation that results in quantitative spectrin deficiency.

Hereditary Xerocytosis: Characterized by red cell membrane abnormality with increased permeability to cations causing a greater efflux of potassium than sodium. Consequently these red cells lose potassium in excess of sodium gained, with a decrease in total cation content. Osmotically resistant xerocytes result. Clinically, the patient may present with episodes of fatigue, jaundice, pallor, and darkened urine, especially during intense physical activity. At the other end of the spectrum from xerocytosis is hereditary stomatocytosis (or hydrocytosis), ...

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