Hair darkening in porphyria cutanea tarda.

Repigmentation of grey hair is rare, but has been described in several clinical settings. It has most often been reported as a postinflammatory effect, but several drugs, chronic arsenic exposure and coeliac disease have also been cited in addition to darkening as a spontaneous phenomenon. We report two patients with sustained repigmentation of the hair in association with porphyria cutanea tarda. The mechanism for this repigmentation remains elusive, but presumably involves recruitment of outer root sheath melanocytes, which are then activated to form functional hair bulb melanocytes.