Abstract: A 35-year-old male patient presented with recurrent high fever for more than 3 months and generalized erythema, blisters, and itching for 2 days, with a positive Nikolsky's sign. Previous examinations revealed cytopenia and abnormal liver function; Mycobacterium kansasii was detected in the lungs. The patient showed poor response to multiple anti-infective agents and developed mucocutaneous lesions. After admission, he was diagnosed with severe erythema multiforme drug eruption. Treatment with glucocorticoids, intravenous immunoglobulin (IVIG), and supportive care resulted in improvement of skin lesions; however, high fever recurred following glucocorticoid tapering. The patient requested discharge and died approximately 1 month later. Combined with fever ≥38.5℃, splenomegaly, cytopenia, hypertriglyceridemia, and ferritin ＞1650 ng/mL, the final diagnosis was hemophagocytic lymphohistiocytosis (HLH). This case indicates that Mycobacterium kansasii infection can induce HLH. The coexistence of severe erythema multiforme drug eruption and HLH indicates a critical condition. Clinicians should maintain high suspicion of HLH in patients with prolonged fever, liver injury, cytopenia, and significantly elevated ferritin, and early identification and standardized intervention are essential to improve prognosis.

Key words: Mycobacterium kansasii, severe erythema multiforme drug eruption, hemophagocytic lymphohistiocytosis