Pemetrexed-induced Sweet Syndrome: First case report in the medical literature.

Introduction: Sweet Syndrome, also known as acute febrile neutrophilic dermatosis, is a rare inflammatory disease characterized by the sudden emergence of painful, edematous, and erythematous papules, plaques, or nodules on the skin, which usually fully responsive to systemic corticosteroids. Skin lesions are often accompanied by fever and leukocytosis. Here we present a case of Sweet Syndrome caused by pemetrexed in metastatic lung adenocarcinoma.

Case Report: A 52-year-old patient with metastatic lung adenocarcinoma received multiple lines of chemotherapy. The patient presented with extensive skin lesions after performing of pemetrexed chemotherapy. He had a fever and elevations in blood levels of C-reactive protein (CRP), sedimentation, leucocytes, and neutrophils. Neutrophil predominant perivascular and interstitial dermatitis, focal micropustule formation, and severe neutrophilic dermatosis were reported in skin biopsy. Topical steroid and oral antihistamine treatment were started as initial treatment. Cutaneous side effects related to pemetrexed are often reported as 'skin rash,' which is a non-specific term. Therefore, the diagnosis of Sweet Syndrome must be confirmed by skin biopsy. It is essential to exclude the presence of an infection and medication history. Recovery in drug-induced Sweet Syndrome occurs after the drug that caused it was discontinued. Systemic corticosteroids are the first-line treatment for most cases.