Mendenhall's syndrome: clues to the aetiology of human diabetic neuropathy.

The pathogenesis of human diabetic neuropathy remains unclear. Mendenhall's syndrome is characterised by a mutation in the insulin receptor gene with consequent lifelong uncontrolled hyperglycaemia. The sural nerve biopsy from a patient with Mendenhall's syndrome showed a gross loss of myelinated fibres that was comparable with the degree of fibre loss in a case matched diabetic patient with established neuropathy. The biopsy from the patient with Mendenhall's syndrome showed only a very mild degree of microangiopathy, however, which failed to relate to the degree of nerve fibre loss and also did not compare with the advanced degree of microangiopathy seen in the diabetic patient. Thus hyperglycaemia itself did not result in appreciable microangiopathy. Furthermore the presence of severe neuropathy without advanced microangiopathy suggests an important and independent role for metabolic factors in the pathogenesis of neuropathy.