[Neuroendorine paraneoplastic syndromes]

Skin is commonly affected by neuroendorine paraneoplastic syndromes (PNS). This is due to the expression of receptors in the skin by which abnormally secreted neuroendocrine hormones and mediators elicit directly, and indirectly, cutaneous key signs and thus facilitate early diagnosis of these diseases. In acromegaly, induction of the growth hormone-insulin-like growth factor‑1 axis results in trophic changes of the acral portions of the skin and mucosal membranes including cutis verticis gyrata. The skin signs of non-iatrogenic Cushing syndrome are identical with those of exogenous prolonged intake of glucocorticoids: centripetal accumulation of adipose tissue, plethora and striae distensae. Episodic flushing of the face and trunk (together with explosive diarrhea) is a key feature of carcinoid tumors. Fibrotic remodeling of the heart and retroperitoneal space, and less commonly of the skin, are important complications mediated by abnormally secreted 5‑hydroxytryptamine (serotonin, 5‑HT), the latter eliciting profibrotic responses on HT_2B-receptor-expressing fibroblasts. Androgen-secreting tumors lead to well-established receptor-mediated cutaneous signs of peripheral hyperandrogenisms: seborrhea, acne, hirsutism, and androgenetic alopecia. In contrast, the pathogenesis of necrolytic migratory erythema as a key feature of glucagonoma remains incompletely understood and is thought to be related to hypoaminoacidemia. This review summarizes the clinical features of neuroendocrine PNS with skin involvement, elucidates its underlying pathophysiology, lists differential diagnoses, and explains key diagnostic steps and principal therapeutic options. An interdisciplinary approach is essential to provide the best care of all patients with neuroendocrine PNS.