Localised hair loss has three common possibilities, alopecia areata, tinea capitis and trichotillomania. In alopecia areata the area of hair loss is complete, the involved area is smoothe and the hairs may be broken at the edges.The bald area is not inflammed. In tinea capitis the area is never completely bare, the hairs are broken, there may be scale on the surface and signs of scalp inflammation. In trichotillomania the hairs may be broken and the pattern of loss is unusual. The scalp may show inflammation around recently traumatically removed hairs.
Management-Take scrapings if scaly for fungal culture and include a few hairs. Do a hairpull test to see if the hairs around the bare area come out from the base with a telogen bulb on the end, a feature typical of alopecia areata.
Rare causes-Incontinentia pigmenti, nevus sebaceous, post tick bite, follicular mucinosis, Ofugi' disease, localised morphea, aplasia cutis, post herpes zoster, meningocoele,
Generalised hair loss The three common causes are androgenetic alopecia, telogen effluvium and generalised alopecia areata. Androgenetic alopecia is by far the commonest cause in both males and females. Females retain the frontal hair line but get considerable thinning behind it. Telogen efluvium follows a fever, general anaesthetic, weght loss or coming off the contraceptive pill or warfarin among other causes. The hair loss is across all the scalp but there are no bald bits! Generalised alopecia areata is a difficult diagnosis as it gives features similar to telogen effluvium but a scalp biopsy will separate the two conditions. Generalised hair loss is an unfortunate side effect of chemotherapy for various cancers.
Specific conditions involving the Hair
Attachments Pediculosis capitis, Piedra
Fragile Hair Menke's disease, Monilethrix, Netherton's syndrome, Pili torti, Trichothiodystrophy
Green hair Copper
Heterochromia Flag sign of Kwashiorkor and Marasmus
Lighter colored hair Phenylketonuria
Loose hair Loose anagen syndrome
Silver Grey hair Chediak-Higashi syndrome
Uncombable Felting, Uncombable hair syndrome
White Forelock Piebaldism, Wardenburg's syndrome
Whitening Canites
Whorled Scalp whorls
Modified from Regional Dermatology Gary M White
