[Genetic diseases of erythrocyte membrane permeability]

A group of genetic disorders of the red cell, appearing as congenital haemolytic anaemias, were first described on morphological bases, due mainly to the presence of stomatocytes. It turned out, however, that the alterations of the shape could widely vary, and even be absent, thereby questionning the classification on the basis of shape. It is now known that the primum movens of the involved disorders is an increase of the passive leak of the potassium ion. As a consequence, the conditions were redefined according to the perturbations regarding the concentrations and the fluxes of the K+ ion, its companion, the Na+ ion, and the resulting change in red cell hydration. Finally, a genetic classification is dawning. We will consider the best documented conditions which have conserved their initial designation for the time being: hereditary stomacytosis with overhydrated red cells, whose hallmark is misleadingly the nearly complete absence of the protein "stomatin"; familial pseudohyperkalaemia and hereditary stomatocytosis with dehydrated red cells. The two last conditions probably share the same gene, recently mapped to chromsome 16. These disorders are rare, however their recognition suffers no error. Proper diagnosis contra-indicates splenectomy, a sheer paradox as concerned congenital haemolytic anaemias. In addition, the genetic diseases of red cell permeability display patho-physiological mechanisms of paramount interest.