Rabson-Mendenhall Syndrome

An extremely rare genetic disorder characterized by severe insulin resistance and craniofacial anomalies, abnormalities of the teeth and nails, and acanthosis nigricans (hyperpigmentation and hyperkeratosis), particularly of the neck, groin, and underarms.

In 1956, S.M. Rabson and E.N. Mendenhall described this familial syndrome comprising insulin-resistant diabetes, pineal hyperplasia, and various somatic anomalies.

Autosomal recessive. A genetic deficiency of insulin receptors. Gene locus at 19p13.3-p.13.2.

The causative mutation(s) reside in the insulin receptor gene with the defect between synthesis of the receptor precursor and insertion of it into the membrane. The severely impaired insulin-binding capacity results in highly insulin-resistant diabetes mellitus.

Dental and skin abnormalities (acanthosis nigricans, truncal hypertrichosis, malpositioned teeth), short stature, coarse facial features with prognathism, abdominal distension, and phallic enlargement. Highly insulin-resistant diabetes mellitus. The pineal body is hyperplastic. Studies of melatonin state show raised melatonin metabolite excretion in the urine, as might be expected with disordered pineal function.

Somatic anomalies present at birth. Diabetes manifests during childhood or adolescence and may result in ketoacidosis and intercurrent infections. Mortality from ketoacidotic coma has been reported. Acanthosis usually decreases in intensity and extent over time. Hypophysectomy has been of short-term benefit, but the problems of insulin resistance persist.

Optimization of blood sugar control via tight monitoring and institution of appropriate insulin therapy. An appropriate assessment and management of coexisting disease is mandatory. Investigations: blood sugar levels, electrolytes, CBC, ECG, chest radiograph. Other investigations will be necessary to evaluate various end-organ function and should be ordered as directed by clinical findings.

Regional techniques, where appropriate, are preferable to general anesthesia, because they usually allow an earlier return to a normal feeding pattern. The stress response to surgery may also be partially obtunded.

There are no known specific implications for this condition.