Abstract: A 69-year-old male presented with a 6-month history of erythema, swelling, and ulceration on the dorsum of his left hand. Prior to the onset, he had a history of iron nail puncture without insect or animal bite. Histopathological examination revealed infectious granuloma. No hyphae or spores were detected on PAS staining, and acid-fast staining was negative. Bacterial culture was positive. PCR amplification and 16S rRNA sequencing confirmed the pathogen as Proteus vulgaris. Based on the above findings, the diagnosis of Proteus vulgaris skin infection was made. The skin lesions completely resolved after 3 months of oral monotherapy with minocycline hydrochloride, and no recurrence was observed during a 2-year follow-up.

Key words: Proteus vulgaris, infectious granuloma, 16S rRNA gene sequencing, minocycline