Neurofibromatous dermal hypoplasia: a clinical, pharmacological and ultrastructural study.

Dermal hypoplasia is reported in three patients with neurofibromatosis. The areas of dermal hypoplasia failed to react to vasodilator stimuli and responded poorly to a vasoconstrictor stimulus. Histology of these lesions showed neurofibromatous tissue and at an ultrastructural level cells resembling perineurial cells were wrapped around dermal vessels. The poor vascular responses seen in these areas of neurofibromatous dermal hypoplasia might be due to the perineurial cells acting as a barrier to diffusion of the pharmacological agents and as a physical perivascular splint.