Reticulate, patchy and mottled pigmentation of the neck. Acquired forms.

Besides the inherited forms of mottled and reticulate pigmentation, a vast number of diseases and trigger mechanisms can lead to acquired pigmentation of the neck. Nonhereditary variants of reticulate and mottled pigmentation can affect the neck as a typical site and therefore may give a diagnostic clue or it can occur sporadically on the neck as well as on other sites. A well-known and important factor in the pathogenesis is exposure to sunlight. Sun-induced pigmentation often presents on the neck and may result from phototoxic, photoallergic and cumulative actinic damage. Frequent forms comprise berloque dermatitis, Riehl's melanosis, poikiloderma of Civatte and tanning bed lentigines. Different infections may also lead to this distinct skin alteration as pediculosis capitis, pityriasis versicolor and syphilis II. Treatment-induced irregular pigmentations may occur after applications of topical agents (e.g. diphenylcyclopropenone), systemic medication (e.g. 5-fluorouracil, chlorpromazine), as a complication of laser resurfacing or as a chronic graft-versus-host reaction. Different neoplasms may also involve the neck. Widespread pigmented basal cell carcinoma, cutaneous T-cell lymphoma, syringolymphoid hyperplasia and histiocytic diseases may lead to reticulated pigmentation. Various other infrequent conditions as connective tissue diseases, malnutrition, lichen planus pigmentosus and others are summarized. The neck, a readily accessible site to medical inspection, may have an underestimated value for the diagnosis of different skin diseases.