Early onset is marked by intrauterine and postnatal growth retardation, hypotrophy of muscle and adipose tissues, acanthosis nigricans (a skin lesion associated with extreme insulin resistance), dental dysplasia, abnormal hair and nails, hirsutism, and acromegaloid facies. A hypertrophic pineal gland has been reported in some cases.
As in leprechaunism (of which Rabson-Mendenhall syndrome may represent a less severe form); the condition is caused by anomalies in both alleles of the insulin-receptor gene (INSR;19p13.3-p13.2).
