Two further British families with the 'cryohydrocytosis' form of hereditary stomatocytosis

We describe two families with the 'cryohydrocytosis' form of stomatocytosis . Both show a mild stomatocytic anaemia with Hb levels of 12-16 g/dl and re ticulocyte counts of 4.3-24%, with very marked autohaemolysis at refrigerat or temperatures and pseudohyperkalaemia as a result of loss of K from red c ells on storage at room temperature. The ouabain + bumetanide-insensitive ' passive leak' K influx showed a 'U'-shaped temperature dependence, with a m inimum at 23 degreesC. In one family, there was consistent variation in hae matological severity within the pedigree. In the other, the parents of the proposita were normal, but all three of her children were affected, consist ent with a new mutation of a dominant condition. Cold storage of the red ce lls led to a very marked increase in osmotic fragility and macrospherocytos is, explaining why a diagnosis of 'hereditary spherocytosis' can easily be reached in these pedigrees.