Hemolytic disease due to membrane ion channel disorders

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Abstract

Purpose of review

To summarize recent findings in the study of the ′hereditary stomatocytoses and allied disorders’, diseases in which the red cell membrane leaks Na+ and K+, disturbing the osmotic homeostasis of the cell.

Recent findings

Recent work has emphasized the diversity of these conditions, especially evident in the variations in temperature dependence of the cation leak. The association between the dehydrated, xerocytic form that maps to chromosome 16, with perinatal ascites is confirmed. Two cases that may represent a new hematoneurologic syndrome have been recognized.

Summary

These leaky-membrane diseases fall into three main categories. The ′dehydrated’ or xerocytic form maps to chromosome 16 and shows a minimal leak, and can show an excess of phosphatidylcholine in the membrane. Some of these xerocytic cases show a syndrome of self-limiting perinatal ascites of unknown cause. A second group shows very variable temperature dependence in the cation leak. The most severe ′overhydrated’ form shows very leaky cells and the 32kD stomatin protein is missing, although the gene is not mutated. This deficiency seems to be the result of a trafficking problem. The protein is associated with cholesterol and sphingomyelin-rich ′rafts’ and may be some kind of partner protein for a membrane-bound proteolytic system.

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