Acute Generalized Exanthematous Pustulosis in a 76-year-Old Man With Neuroendocrine Carcinoma of the Lung, Responsive to Ixekizumab.

Acute generalized exanthematous pustulosis (AGEP) is a rare, painful, and pruritic drug-induced rash characterized by sterile pustules on an erythematous base, followed by desquamation. While commonly induced by antibiotics, cases associated with antineoplastic drugs have become more frequent in recent years. Here, we report a 76-year-old Chinese male with lung large-cell neuroendocrine carcinoma who developed erythema and pustules on his left lower leg, which spread to the trunk and limbs after the fourth cycle of immunotherapy and chemotherapy. Despite initial treatments with antihistamines, antibiotics, and systemic glucocorticoids, the patient's condition worsened with the development of extensive pustules and fever. Histopathological and laboratory findings confirmed AGEP, with elevated IL-17 levels. Following the discontinuation of immunotherapy and administration of the anti-IL-17 monoclonal antibody ixekizumab, the patient showed rapid improvement within 5 days, marked by a significant reduction in pustules and normalization of body temperature. This case underscores the role of IL-17 in AGEP's pathogenesis and suggests that IL-17 inhibitors such as ixekizumab may provide an effective treatment option for severe, refractory cases.