Diseases solely or predominantly affecting the dermis include tumours derived from the cells of the dermis, various connective tissue diseases, and many of the cutaneous manifestations of systemic diseases (Chapter 8). Tumours involving the dermis may be benign or malignant, and sometimes provide the most obvious clinical features of inherited diseases, such as neurofibromatosis and tuberous sclerosis. The diagnosis of dermal disorders in deeply pig-

mented skin does not usually present particular difficulties, since the level of pathology in the skin can often be established by palpation. However, difficulty in perceiving colour changes in black skin may pose diagnostic problems. For example, the purplish hue of vascular lesions is not seen in deeply pigmented skin and T-cell lymphoma is likely to present with persistent hyperpigmented or hypopigmented plaques or tumours rather than with erythematous plaques.