Certain follicles of the scalp regress with age to produce tine vellus instead of coarse terminal hairs. This patterned baldness often starts as temporal recession, progressing to thinning of hair over the crown. It is common in males and is androgen dependent, prevented by prepubertal castration but not reversed by castration in maturity. Temporal recession is less common in women and may suggest virilisation. Loss or thinning of hair over the frontal region is an almost constant finding in the rare condition myotonic dystrophy, and is also seen in systemic lupus erythematosus.
Alopecia is the term used to describe hair loss. It has many causes and pallems. Complete hair loss may occur following the administration of some cytotoxic drugs. The most common local disease of the hair of the scalp is alopecia areata, in which the hair falls out in patches. In active spreading alopecia areata, hairs shaped like exclamation marks (Fig. 2.12| arc found at the periphery of the bald area, which is clean and smooth. Alopecia areata may rarely cause total seal]) baldness (alopecia totalis) or loss of all body hair (alopecia universalis), both distressing conditions. Alopecia may also be caused by a fungal infection. In this condition, the affected area contains hairs infection. In this condition, the affected area contains hairs
broken off close to the skin. In assessing alopecia it is helpful to distinguish if the hair loss is due to an abnormality of the hair shaft (as in some inherited disorders of sparse hair) or of the scalp and. if the latter, whether or not there is evidence of scarring. A search for nits and licc is essential in patients with an itchy scalp and posterior cervical lymphadenopathy. Nits (the ova of lice) are firmly adherent to the hair shaft, whereas dandruff (desquamating scalp scales) is easily shed.
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