Rabson-Mendenhall syndrome is a rare congenital condition characterized by severe insulin resistance, developmental abnormalities, and acanthosis nigricans.^[1] A hypertrophic pineal gland has been reported in some cases.^[2]

As in leprechaunism, of which Rabson-Mendenhall syndrome may represent a less severe form, the condition is caused by molecular modification of both alleles of the insulin-receptor gene.

The condition is transmitted as an autosomal recessive trait and mainly affects children of consanguineous parents.^[2]

Rabson and Mendenhall described 3 siblings (2 girls, 1 boy) who initially presented with dental and skin abnormalities, abdominal distention, and phallic enlargement.^[3] The children demonstrated early dentition, a coarse, senile-appearing facies, and striking hirsutism. An “adult growth of hair of head” at 5 years of age was pictured in the case of one of the girls. In the older girl the genitalia were large enough at the age of 6 months to permit vaginal examination for diagnosis of a left ovarian tumor which was removed soon afterward. The children were mentally precocious. Prognathism and very thick fingernails as well as acanthosis nigricans were also described. Insulin-resistant diabetes developed, and the patients died during childhood of ketoacidosis and intercurrent infections. At necropsy pineal hyperplasia was found in all three.^[3]

Biologically, infants display fasting hypoglycemia, postprandial hyperglycemia and hyperinsulinemia, which progress to permanent hyperglycemia and recurrent diabetic ketoacidosis.

Cochran et al. reported that treatment of 2 sibs with Rabson-Mendenhall syndrome with pharmacologic doses of human leptin resulted in improvement of fasting hyperglycemia, hyperinsulinemia, basal glucose, and glucose and insulin tolerance.^[4]

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