spherocytosis can occur without cation leaks. These include cases of phytosterolemia nonleaky stomatocytosis, a disorder of lipid metabolism associated with mutations in ABCG5 and/or ABCG8, which encode sterol transporters. The resulting abnormal sterol composition of erythrocyte cell membranes causes them to appear as deformed stomatocytes on peripheral blood smear. Diagnosis Ektacytometry may be helpful in distinguishing different subtypes of hereditary stomatocytosis. Variants Haematologists have identified a number of variants. These can be classified as below. Overhydrated hereditary stomatocytosis Dehydrated hereditary stomatocytosis (hereditary xerocytosis; hereditary hyperphosphatidylcholine haemolytic anaemia) Dehydrated hereditary stomatocytosis with perinatal edema and/or pseudohyperkalemia Cryohydrocytosis 'Blackburn' variant Familial pseudohyperkalaemia (not associated with hemolytic anemia) There are other families that do not fall neatly into any of these classifications. Stomatocytosis is also found as a hereditary disease in Alaskan malamute and miniature schnauzer dogs. Treatment At present there is no specific treatment. Many patients with hemolytic anemia take folic acid (vitamin B9) since the greater turnover of cells consumes this vitamin. During crises transfusion may be required. Clotting problems can occur for which anticoagulation may be needed. Unlike hereditary spherocytosis, splenectomy is contraindicated. References Further reading External links Hereditary hemolytic anemias