Hair disorders associated with autoimmune connective tissue diseases.

Hair disorders are frequently observed in various systemic diseases, including autoimmune connective tissue diseases (CTDs), with predilection of lupus erythematosus (LE), followed by dermatomyositis (DM) and scleroderma. Hair disorders in CTDs may manifest as various clinical patterns, such as telogen hair loss, diffuse thinning or fragility of hair, and scarring alopecia. Less common hair disorders include anagen effluvium, alopecia areata, and trichomegaly. Some drugs used to treat CTDs may cause hair loss in a drug-related manner or hyperthrichosis. In the assessment of common hair loss patterns, such as telogen effluvium, the possible association with CTDs must be borne in mind and should not be overlooked. Alopecia appears to be a significant sign in the course of LE and especially systemic LE. In DM, the involvement of the scalp is common, and is often characterized by a diffuse, violaceous, scaly, non-scarring and symptomatic hair loss. Linear scleroderma en coup de sabre is an uncommon localized form of morphea with involvement of the paramedian forehead and frontal scalp, where it is associated with cicatricial alopecia. The most important variant of scarring alopecia in the context of CTDs is that associated with discoid lupus erythematosus (DLE). In the diagnostic work-up of DLE-related cicatrical alopecia, histopathological and immunopathological studies are useful, and a relevant role has been attributed to dermatoscopy (trichoscopy) over the last years. Hair loss has been reported in several other CTDs, including mixed and undifferentiated CTDs, and primary Sjögren's syndrome, although it is likely to be underestimated in such diseases.