Poliosis circumscripta, commonly referred to as a "white forelock", is a condition characterized by localized patches of white hair due to a reduction or absence of melanin in hair follicles. Although traditionally associated with the scalp, poliosis can affect any hairy area on the body, including eyebrows, eyelashes, and beards. Microscopically, poliosis is marked by the lack of melanin or melanocytes in the hair bulbs, though epidermal melanocytes typically remain unaffected unless associated with conditions like vitiligo.

Etiology

Genetic causes

Poliosis can be congenital and often occurs in the context of various genetic syndromes. These disorders are typically linked to other systemic manifestations.

Acquired causes

In addition to genetic factors, poliosis can develop due to various inflammatory, autoimmune, or neoplastic conditions, or as a side effect of medication.

Differential Diagnosis

Several genetic and acquired disorders can mimic poliosis, and they should be considered during diagnosis:

Associated medical conditions

Poliosis occurs in several genetic syndromes such as piebaldism, Waardenburg syndrome, neurofibromatosis type I, and tuberous sclerosis. It can also occur in conditions such as vitiligo, Vogt–Koyanagi–Harada disease, alopecia areata, and sarcoidosis, and in association with neoplasms and some medications.

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