Scarring alopecia Hair follicles can be damaged in many ways. If the follicular openings can no longer be seen with a lens, regrowth of hair cannot be expected. Sometimes the cause is obvious: a severe burn, trauma, a carbuncle or an episode of inflammatory scalp ringworm. Discoid lupus erythematosus (p. 123), lichen planus (p. 64) and morphoea (p. 129) can also lead to scarring alopecia. The term pseudopelade is applied to a slowly progressive non-inflamed type of scarring which leads to irregular areas of hair loss without any apparent preceding skin disease. If inflammation is present, a biopsy may help to establish the diagnosis. Diffuse hair loss Hair is lost evenly from the whole scalp; this may, or may not, be accompanied by a thinning visible to others (Fig. 13.12). Some of the most common causes are listed in Table 13.2, but often a simple explanation cannot be found. Table 13.2 Some causes of diffuse hair loss. Telogen effluvium Endocrine hypopituitarism hypoor

13.12 Diffuse hair loss causing much anxiety. REGIONAL DERMATOLOGY 169 In other inherited disorders the hair may be beaded and brittle (monilethrix); flattened and twisted (pili torti); kinky (Menkes syndrome caused by mutations in a gene encoding for a copper transporting membrane protein); like bamboo (Nethertons syndrome, caused by a gene on chromosome 5q32 encoding a serine protease inhibitor); partly broken in many places (trichorrhexis nodosa); woolly or uncombable. Differential diagnosis This is from other types of diffuse hair loss (Table 13.2). Treatment This condition is unaffected by therapy, but patients can be reassured that their hair fall will be temporary. Other causes of diffuse hair loss The causes mentioned in Table 13.2 should be

If no cause is obvious, it is worth checking the haemoglobin, erythrocyte sedimentation rate (ESR), ANF, serum iron, thyroxine and thyroid-stimulating hormone (TSH) levels. Also consider checking the serum free testosterone and dihydroepiandrosterone sulphate levels in women with menstrual irregularities or hirsutism. However, it is true to say that often no cause for diffuse alopecia can be found. LEARNING POINTS 1 Be sympathetic even if the hair loss seems trivial to you. 2 Reassure your patient that total baldness is not imminent. Fig. 13.13 Hypohidrotic ectodermal dysplasia: minimal scalp hair and characteristic facies. Fig. 13.14 The cone-shaped incisors of hypohidrotic ectodermal dysplasia. Rare genetic causes of hypotrichosis More than 300 genetic conditions exist that have hair abnormalities as one component. The hypohidrotic ectodermal dysplasias are a group of rare inherit

(Figs 13.13 and 13.14). Heat stroke may follow inadequate sweat production. One type is inherited as an X-linked recessive. The responsible gene for this type (on chromosome Xq12) has recently been shown to encode for a protein (ectodysplasin) involved in the regulation of ectodermal appendage formation. The genes responsible for the dominant/recessive types encode for the ectodysplasin receptor. 170 CHAPTER 13 Hirsutism Cause Some degree of hirsutism may be a racial or familial trait, and minor facial hirsutism is common after the menopause. In addition, some patients without a family background of hirsutism become hirsute in the absence of any demonstrable hormonal cause (idiopathic hirsutism). Finally, some patients with hirsutism will have one of the disorders shown in Fig. 13.17. Presentation An excessive growth of hair appears in the beard area, on the chest and shoulder-t