Genotypic/phenotypic heterogeneity of selective vitamin B12 malabsorption (Grasbeck-Imerslund syndrome) in two Bedouin families.

We report on seven patients in two unrelated consanguineous Bedouin families with Grasbeck-Imerslund syndrome. Pedigree analysis in Family 1 was suggestive of an X-linked mode of inheritance. Intra- and inter-familial heterogeneity was elicited among the affected children in both families. Two of the affected sibs in each family had raised Hb A2 (>4%) while a third in Family 1 had a raised level of Hb F before treatment. One of the patients developed subacute combined degeneration of the cord at the age of 17 years before the correct diagnosis was made. All abnormalities were corrected following the institution of parenteral cobalamin therapy.