Hereditary Xerocytosis

At a glance

Hereditary xerocytosis is characterized by red cell membrane abnormality with increased permeability to cations and a greater efflux of potassium than of sodium. It is a rare, autosomal dominant congenital hemolytic anemia characterized by macrocytic stomatocytosis, and decreased red cell osmotic fragility due to a defect in cation permeability. 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), in which the red cells are overhydrated and sodium loaded.

Synonym

Hereditary Hyperphosphatidylcholine Hemolytic Anemia; Dehydrated Hereditary Stomatocytosis; Hereditary Desiccytosis.

Incidence

Approximately 1:10,000 kindreds in France and the United Kingdom.

Genetic inheritance

Autosomal dominant. Mutation located on chromosome 16, but the gene is not yet identified. Hereditary xerocytosis differs from other stomatocytoses in that the stomatin protein (or “erythrocyte membrane protein 7.2b”) is not missing from the red cell membrane.

Pathophysiology

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

Diagnosis

Laboratory findings include hemoglobinuria, increased red cell hemolysis by shear stress, increased mean corpuscular volume, and increased mean corpuscular hemoglobin concentration.

Clinical aspects

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. Transfusions are generally not required, and the benefit of splenectomy is slight. Iron overload may develop later in life.

Precautions before anesthesia

Check hemoglobin level and reticulocyte count.

Anesthetic considerations

Potential reduction in oxygen delivery as a consequence of decreased levels of 2,3-diphosphoglycerate.

Pharmacological implications

No known specific implications with this condition.

Other conditions to be considered

• ☞Hereditary Spherocytosis: Genetically transmitted hemolytic anemia caused by mutations in the spectrin gene in people of circum-Mediterranean descent. Autosomal dominant and recessive forms are described.

• ☞Hereditary Stomatocytosis: Series of inherited red blood cell disorders in which the outer membrane of the cell “leaks” sodium and potassium.

• Hereditary Pyropoikilocytosis: Autosomal dominant hemolytic medical condition in which erythrocytes have a bizarre morphology similar to that seen in thermal burns. Probably ...