Woolly hair is a rare congenital abnormality related to the structure of scalp hair, which is characterized by tightly curled, thick, and fragile hair. It can occur as an isolated anomaly or in association with Carvajal syndrome or Naxos disease.
Woolly hair is an inherited disorder; it shows an autosomal dominant or autosomal recessive pattern. In the autosomal dominant variation (ADWH), patients exhibit strong and inconstant degree of tight curling hair throughout the scalp at birth or in the few months of life, but it has no effect on the pigmentation of the hair. Manifestations of ADWH are also noted to become significantly less severe in adulthood.
ADWH is associated with mutations in the KRT74 gene. KRT74 gene plays an important role in hair formation and encodes Cytokeratin-74, which is expressed in the inner root sheath of hair follicles.
Madi et al. (2005) investigated 7,739 live and still-born babies during the period from January 2000 to December 2001 in Al-Jahara Hospital in Kuwait. Of these, 97 babies suffered from major congenital abnormalities, suggesting an incidence of about 12.5 per 1000 birth. One of the babies was affected with Woolly hair disease.
Al-Harmozi et al. (1992) described a male patient with wolly hair nevus syndrome, in which the hair within a well-demarcated area is lighter than the normal hair and has a reduced diameter.