Four pedigrees of the cation-leaky hereditary stomatocytosis class presenting with pseudohyperkalaemia. Novel profile of temperature dependence of Na+–K+ leak in a xerocytic form

Summary We report four pedigrees of the group of Na+?K+-leaky red cell disorders of the ?hereditary stomatocytosis? class. Each showed pseudohyperkalaemia because of temperature-dependent loss of K+ from red cells on storage of whole blood at room temperature. All pedigrees showed an abnormality in the temperature dependence of the ?passive leak? of the membrane to K+. Two pedigrees, both of which showed a compensated haemolytic state with dehydrated red cells and target cells on the blood film, showed a novel pattern, in which the profile was flat between 37°C and about 32°C then dropped as the temperature was reduced to zero. The third showed the ?shallow slope? profile, with stomatocytes on the blood film and very markedly abnormal intracellular Na+ and K+ levels. Minimal haemolysis was present. The fourth pedigree, of Asian origin, showed the shoulder pattern (minimum at 32°C, maximum at 12°C) with essentially normal haematology. Both of these latter two forms have previously been seen in other pedigrees. The first variant represents a novel kind of temperature dependence of the passive leak found in these pedigrees presenting with pseudohyperkalaemia.