NIH

Zebra of the Week: Woolly hair nevus

March 31, 2025

An epidermal nevus is a benign patch of skin caused by an overgrowth of skin cells. Thees nevi are seen at birth or develop in early childhood. They can be flat, tan patches of skin, or raised, velvety patches and may become thicker and darker and develop a verrucous appearance.

Often, woolly hair nevi follow a pattern on the skin known as the 'lines of Blaschko.' Patients with woolly hair nevus may present with associated systemic abnormalities, including neurological, ophthalmological, and skeletal manifestations. This collection of symptoms is referred to as woolly hair nevus syndrome, encompassing a spectrum of disorders that affect multiple organ systems. Genetic changes associated with a woolly hair nevus are present only in the cells of the nevus, not in the normal skin cells surrounding it, and may involve the FGFR3, PIK3CA or, HRAS genes.

Sources:

NIH GARD. Accessed 2025, March 28). Woolly hair nevus. https://rarediseases.info.nih.gov/diseases/13025/wooly-hair-nevus

Venugopal V, et al. (2012). Int J Trichology. Woolly hair nevus: A rare entity [Image]. https://pmc.ncbi.nlm.nih.gov/articles/PMC3358940/