Circumscribed hypertrichosis triggered by exogenous provocation (e.g. repeated chemical or physical trauma) or provoked by fractures and nerve injuries or associated with various diseases (e.g. scleroderma, progressive systemic; scleroporphyria).
Occurrence as an adverse drug reaction in drug treatment, described for azelaic acid, interferon alfa, glucocorticoids, psoralene (see below methoxsalen), ACTH, streptomycin, phenytoin, minoxidil, diazoxide, ciclosporin A, penicillamine and danazol.