Dehydrated hereditary stomatocytosis mimicking familial hyperkalaemic hypertension: clinical and genetic investigation.

Dehydrated hereditary stomatocytosis (DHS) is a rare dominant form of hereditary haemolytic anaemia. In some families, pseudohyperkalaemia accompanies DHS. Familial hyperkalaemic hypertension (FHHt), a rare autosomal dominant form of arterial hypertension, is associated with genuine hyperkalaemia. We present a large French family in which DHS and FHHt were diagnosed independently in two separate branches. In branch A, mild DHS accompanied by pseudohyperkalaemia was found. In branch B, the proband and her daughter were initially diagnosed with FHHt, based on the coincidence of high blood pressure and hyperkalaemia. After finding out that branches A and B were related, reinvestigation of the affected members of branch B lead to the diagnosis of DHS, yielding the largest DHS kindred known in France. This allowed extensive linkage analysis based on 19 microsatellites markers in 12 affected and 10 unaffected members at 16q24.1qter, where one known DHS locus maps to. A maximal two-point LOD score (4.71 at theta = 0) was obtained for markers D16S3074 and D16S476. Haplotype analysis led to the definition of a new 11.5 cM disease interval with an upper limit at microsatellite D16S3037.