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Woolly hair nevus - Hair and Scalp
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Woolly hair nevus - Hair and Scalp

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Contributors: Amy Fox MD, David Dasher MD, Mary Gail Mercurio MD, Jeffrey D. Bernhard MD, Lowell A. Goldsmith MD, MPH
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Synopsis

Woolly hair nevus (alternatively spelled wooly hair nevus) is a localized alteration of scalp hair often presenting at birth or in the first several years of life. Its localized nature will differentiate this nevus from other inheritable conditions including hereditary woolly hair and uncombable hair.

(Hereditary woolly hair is a rare abnormality characterized by extreme kinkiness of hair in those who are not of African descent. [This hair texture is considered normal in most black patients.] The hair shaft is tightly coiled and exhibits an elliptical cross section. It may be more fragile. Inheritance is usually autosomal dominant with a much rarer autosomal recessive form. Its manifestations often become less severe in adulthood.) 

Classically, the hair in woolly hair nevus is described as curly, smaller in diameter, and often lighter in color. There are no pathognomonic trichogram features.

Woolly hair nevus is often found associated with epidermal nevi or pigmented nevi, most often of the neck or upper extremities. It can also be associated with ocular findings including papillary membranes and retinal abnormalities.

Rarely, woolly hair nevus has been described in association with various syndromes including Noonan syndrome and cardiofaciocutaneous syndrome. A few cases of woolly hair nevus in patients with incontinentia pigmenti have been reported.

Codes

ICD10CM:
Q84.1 – Congenital morphological disturbances of hair, not elsewhere classified

SNOMEDCT:
239124001 – Woolly hair nevus

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Hereditary woolly hair – If the patient has a large woolly hair nevus, this can be difficult to distinguish. Look for nevus to have circumscription and lack of family history.
  • Uncombable hair syndrome – Silvery hair with texture of "spun glass." This will be a diffuse condition involving the entire scalp. A positive family history may be uncovered.
  • Pili torti – Can have focal areas of shortened, brittle hair with characteristic trichogram features; flattened and twisted hair.
  • Trichorrhexis nodosa (TN) – Because the hair may be more fragile, concomitant TN is common, but close evaluation demonstrating the tight coiling should make it clear that the TN is a secondary phenomenon.

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Last Updated: 08/01/2017
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Woolly hair nevus - Hair and Scalp
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Woolly hair nevus : Occipital scalp, Parietal scalp, Unruly hair
Clinical image of Woolly hair nevus
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