Familial hyperinsulinaemia associated with epilepsy and mental retardation--a syndrome of familial insulin resistance.

BACKGROUND

Variants of type A insulin resistance, characterized by female hyperandrogenism and 'acromegaloid' features, have been ascribed to genetic defects of the insulin receptor or post-receptor pathways via autosomal dominant or recessive inheritance patterns. Whilst a variety of congenital syndromes of insulin resistance are identified by their characteristic clinical phenotypes, an association with epilepsy and mental retardation has not previously been reported.

CASE REPORT: We describe three female siblings (aged 12, 19 and 21) with fasting hyperinsulinaemia (116-443 pmol/l; normal range < 80 pmol/l) and mental retardation. Two siblings also have epilepsy. The eldest has features of severe insulin resistance with dyslipidaemia, acanthosis nigricans, 'acromegaloid features' and diabetes requiring high dose insulin therapy in combination with a glitazone. Their mother has fasting hyperinsulinaemia (113 pmol/l), mental retardation and epilepsy. None had clinical or biochemical features of hyperandrogenism or evidence of pigmentory retinopathy, deafness or renal insufficiency. Autoantibody screens were negative. Interestingly, there is no evidence of mental retardation or epilepsy among males in the family.

CONCLUSION

This family suggests the presence of a yet-undefined syndrome of familial insulin resistance affecting female kindred. Further studies are being undertaken to clarify the genetic defects and mode of inheritance.