Abstract: This paper reports a case of skin infection with Alternaria. The patient had been treated with oral orelabrutinib for 2 years for chronic myeloid leukemia. He presented with dark red infiltrative plaques and ulcers appeared on the right lower limb for 3 months. The patient had been treated with oral and topical medications in a local hospital (specific diagnosis and medication are unknown), but there was no significant improvement, so he was treated in our hospital. The initial diagnosis was pyoderma gangrenosum, and the patient was recommended to undergo pathological examination. The pathology showed infectious granuloma, PAS staining showed round spores and hyphae in the dermis, fungal microscopy was positive, and fungal culture Alternaria grew, and the patient was diagnosed with skin Alternaria infection. The patient was cured after itraconazole combined with topical sertaconazole cream.

Key words: Alternaria, skin infection