By Gary M. White, MD
A woolly hair nevus (WHN) is a congenital localized area of curly hair among straight hair.
A localized area of curly hair is characteristic of the WHN. Onset is usually within the first two years of life. The WHN may also present as a congenital patchy area of alopecia, which later evolves into a WHN. The abnormal hair may be finer and lighter that the surrounding normal hair and may be more difficult to comb. On light microscopy, the woolly hair's diameter is significantly reduced and its cross-section oval. Woolly hair may also occur diffusely.
An epidermal nevus underlying the curly hair or located elsewhere may be associated. Extracutaneous abnormalities associated with WHN have been described, but usually in the case of an associated epidermal nevus and the epidermal nevus syndrome.
There is no effective treatment although the condition may improve over time.
Pachyonychia congenita with woolly hair in a ten-month-old infant. Indian J Dermatol Venereol Leprol 2008;74:485-6
A 14-year-old boy born without any abnormalities initially had normal hair. However, after the shedding of neonatal hair, new hair grew extremely slowly and scarce, with a woolly appearance. He also developed a dilated cardiomyopathy. Acta Dermato-Venereologica 2015;95;337
Great picture of a patch of wooly hair in a 3-year-old healthy girl. Int J Trichol 2014;6:187-8
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