Alpha thalassaemia/mental retardation syndrome (non-deletional type): report of a family supporting X linked inheritance.

In 1990 the existence of an X linked form of the alpha thalassaemia/mental retardation syndrome was postulated after the description of six isolated cases who were all cytogenetically male. The segregation pattern in the family described here supports X linked inheritance. The clinical details of our two patients are remarkably similar to the previously delineated phenotype. In addition, renal anomalies were identified in one patient, but their significance will remain uncertain until further cases have been assessed. Affected subjects could be identified by the presence of Hb H inclusions, and were also noted to have abnormalities of several haematological indices. Examination of blood from obligatory carriers in this family suggests that Hb H inclusions are not an invariable finding and that haematological indices appear to be unaffected by the condition in female heterozygotes.