- Alopecia areata: light and electron microscopic pathology of the
regrowing white hair.
Messenger AG, Bleehen SS
Light and electron microscopic studies have been carried out on fifteen regrowing white
anagen hair follicles from seven patients with alopecia areata. Seven bulbs showed
evidence of cell injury that was concentrated in cortical keratocytes. Lower bulb matrix
cells appeared undamaged though in six bulbs apoptotic degeneration was seen in the lower
bulb keratocytes, perhaps indicating early catagen transformation. Melanocytes were
identified in all the bulbs except those from one patient. The number of melanocytes and
their melanization were much less than in the normal pigmented follicle, and pigment
transfer was rarely seen. It is proposed that alopecia areata is a disease of
differentiating cortical keratocytes. The failure of pigmentation in the regrowing white
hair may be post-inflammatory, but the various other pigmentary features of alopecia
areata, especially the sparing of senile white hairs, suggest that pigmentary mechanisms
in the hair bulb are of primary importance in the pathogenesis of this disorder.