Pseudohyperkalaemia and pseudomacrocytosis caused by inherited red-cell disorders of the 'hereditary stomatocytosis' group

Unusual dominantly inherited conditions of the red cell, collected under th e generic title 'hereditary stomatocytosis and allied disorders', exist, in which the red cell 'leaks' the univalent cations sodium (Na+) and potassiu m (K+). In some kindreds with these disorders, bizarre temperature effects can occur that have profound effects on the way in which the cells behave w hen removed from the body and cooled to either room or refrigerator tempera tures. In some types, the cells lose K+ at room temperature, giving rise to pseudohyperkalaemia; in others, this occurs in concert with swelling of th e red cell and pseudomacrocytosis. In some of these conditions, a red-cell abnormality is clearly demonstrated by the presence of haemolytic anaemia; however, routine haematology can be virtually normal in the milder versions . All are inherited as dominants, although new mutations can be seen.