The non-deletion alpha thalassaemia/mental retardation syndrome: further support for X linkage.

It has previously been suggested that the non-deletion form of the alpha thalassaemia/mental retardation syndrome may be an X linked disorder. We describe four brothers with this syndrome in whom the diagnosis was first suspected because of their characteristic clinical features, although these varied somewhat from one sib to another. The diagnosis was confirmed in each case by showing Hb H inclusions in a proportion of their red blood cells. The identification of four similarly affected boys in this pedigree is consistent with an X linked pattern of inheritance. In support of this, very rare Hb H inclusions could be found in the red blood cells of the mother and one sister who both share some facial features with the affected boys and are presumably carriers of this disorder. This pedigree thus provides further evidence that this is an X linked syndrome and indicates the clinical and haematological variability that may exist even within a single affected family.