Localized acquired hypertrichosis following cast application

Figure 1: Localized hypertrichosis on right forearm with traumatic scar.

Figure 1: Localized hypertrichosis on right forearm with traumatic scar.

Sir,

Hypertrichosis in general means growth of hairs involving non-androgen dependent follicles that is considered excessive for the site and the age of a patient. ^[1] It can be divided into localized (congenital or acquired) or generalized (congenital or acquired). Localized hypertrichosis can be because of various reasons which may be due to repeated or prolonged inflammatory changes involving the dermis. Increased hair growth following cast application is an uncommonly reported phenomenon, though well known to orthopaedic surgeons. ^[2]

A-9-year-old girl presented with increased hair growth localized only on right forearm since the last 15 days. She had a history of trauma due to fall from a bicycle leading to fracture of the lower third of forearm bone (radius). An orthopedic surgeon had treated her with a below-elbow plaster of Paris cast on right forearm for 4 weeks. Subsequent to this, excessive hair growth was noticed on that area following the removal of cast. There was no history suggestive of topical applications or drug intake, except oral analgesics for two days and a five day course of oral cefadroxil. On cutaneous examination, there was increase in fine and coarse hair on right forearm as compared to the other side, with post traumatic scar on extensor aspect of the same area [Figure - 1]. No hypertrichosis was seen on the rest of the body. Systemic examination and routine laboratory parameters were within normal limits.

Circumscribed hypertrichosis has been observed following repeated friction as on the shoulder of sack bearers or on sites of infection or inflammation such as thrombophlebitis, chronic osteomyelitis or vaccination sites, around the edges of a burn and near inflamed joints in association with gonococcal arthritis. ^[2],[3],[4] A temporary overgrowth of hairs can be seen in inflammatory dermatoses like after eczema and varicella. ^[5] Hypertrichosis of one leg or forearm after a prolonged period of occlusion by plaster of Paris is a phenomenon not very commonly described in dermatological literature. Local increase in blood flow around fracture site and increased metabolism on the part of all local soft tissues may be the probable reason of localized increased hair growth after cast application. Other authors also postulated that cutaneous hyperemia may be responsible for hypertrichosis in their cases. ^[6],[7],[8] The condition which has cosmetic significance, generally resolves within six months. ^[8]