ABSTRACT
DEFINITION AND CLINICAL FEATURES Hyperpigmented, velvety plaques involving neck and flexures. Acanthosis nigricans has several causes and the common mechanism is likely to be stimulation of growth factor signalling pathways in the epidermis. This may occur in insulinresistant syndromes due to increased stimulation of insulin-like growth factor receptors. Benign forms of acanthosis nigricans are characterized by the insidious onset of brown, thickened papillomatous skin predominantly affecting the nape of the neck (303) and axillae (304); less commonly, the anogenital and groin regions are also involved. Features suggestive of underlying malignancy include rapid onset, extension to extraflexural sites, involvement of mucous membranes and/or vermilion border, presence of deeply pigmented, verrucous plaques, associated palmar keratoderma, and nail changes. The disorder is divided into five main subgroups according to their underlying aetiology:
• Hereditary – benign autosomal dominant. • Benign – caused by endocrine disorders,
including acromegaly, Addison’s disease, Cushing’s disease, diabetes mellitus.
