Comment on Scalp Neuropathy in Androgenetic Alopecia

The authors of this paper investigated the hypothesis of scalp neuropathy in androgenetic alopecia (AGA). They evaluated scalp sensation in men with different levels of hair loss and found that neuropathy with decreases in pressure sensitivity and 2-point discrimination at the vertex of the scalp was significantly associated with AGA. However, no association was found between AGA and temperature discrimination. The authors suggest that the attachment of the arrector pili muscle to the hair follicle and its innervation may maintain follicular integrity, and the inability to contract the muscle might provoke hair loss. They also discuss the role of nerve fibers and neuropeptide substance P in hair follicle innervation. The authors acknowledge that their study shows association rather than cause and effect. They conclude that further studies using ultrastructural and immunohistochemical techniques are needed to verify the presence of neuropathy in AGA. The authors also criticize the analogy made between hair loss in AGA and leprosy, stating that it is stigmatizing and not supported by evidence.