Congenital hypertrichosis (CGH) is a rare inherited condition characterized by excessive hair growth on the body present at birth. People who are affected with this disease are often stigmatized, yet have been an intriguing subject not only in the field of science and genetics, but for circus and royalty amusement in the Middle Ages. Rashid and White (2007) first distinguish between the three types of human hair associated with CGH and the progression of the hair growth. Lanugo hairs are thin, lightly pigmented hairs which develop during the fetus stage of life; they typically shed prior to birth and/or shortly after. Replacing the lanugo hairs are non-pigmented vellus hairs that are shorter in length. Vellus hair covers the entire body with the exception of the scalp, eyelashes and eyebrows. From vellus hair follicle sprout longer and coarser terminal hair. Terminal hair is typically more darkly pigmented and constitutes the eyebrows, eyelashes, and scalp. Terminal hair also arises from the excretion of androgen, or male hormones, during and after puberty, and is thus responsible for the surfacing hair patterns of puberty that are observed.
The different syndromes with CGH as the main phenotypic feature are classified based on the type of hair as well as its distribution (Sun et al., 2009). The most commonly researched CGH is that which is observed over the entire body, referred to as generalized congenital hypertrichosis. Thus far, research shows an inversion on chromosome 8. Balducci et al. (1998) reported a paracentric inversion on chromosome 8, inv8(q12q22). Paracentric inversions are those which do not involve the centromere of the chromosome, showing both breakpoints of the inversion on the same arm.
CGH cannot be readily identified and diagnosed on a molecular basis, but because of its distinct phenotypic characteristics can often be diagnosed based on hair type, distribution and age of onset. Furthermore, CGH is often classified with regard to associated anomalies. Case reports, of both single and multiple generations, have associated CGH with various phenotypic anomalies and other disorders. Phenotypically, observed patients of different syndromes of CGH tend to show characteristic broadened nose and jaw structures, full lips, and a short and broad neck.
The phenotypic defects caused by CGH have significant psychological effects on adolescents and young adults. Those who are affected typically suffer from anxieties and insecurities regarding their physical appearance (Hawryluk & English, 2009). Although there is no cure for this rare disorder, the excess or undesired hair caused by CGH can typically be removed via laser hair removal, waxing, tweezing and most commonly, shaving (Plantin, Schloenlaub, Dupre & LeFlur, 1998).
Balducci R, Toscano V, Tedeschi B, Mangiantini A, Toscano R, et al. 1998. A new case of Ambras syndrome associated with a paracentric inversion (8) (q12; q22). Clin Genet. 53: 466-468.
Hawryluk EB, English JC. 2009. Female adolescent hair disorders. J Pediatr Adolesc Gynecol. 22:271-281
Plantin P, Schoenlaub P, Dupre D, LeFur J. 1998. Shaving: a simple and effective treatment for moderate congenital hypertrichosis. Eur J Dermatol. 8(3): 189-190.
Rashid RM, White LE. 2007. A hairy development in hypertrichosis: a brief review of Ambras syndrome. Dermatol Online J. 13(3): 8.
Sun M, Li N, Dong W, Chen Z, Lui Q, et al. 2009. Copy-number mutations on chromosomes 17q24.2-q24.3 in congenital generalized hypertrichosis terminalis with or without gingival hyperplasia. Am J Hum Genet. 84(6): 807-813.