MRCP2-1000
A 38-year-old pet shop owner presents to the dermatology clinic with lesions on his right hand. He reports noticing a lump over his 2nd metacarpophalangeal joint 2 months ago, which has since increased in size and crusted over, and additional similar lesions have appeared. He denies experiencing pain or itching and has attempted to treat the lesions with various topical emollients without success. The patient has no significant medical history or allergies.
Upon examination, multiple crusted lesions measuring 1-2 cm in diameter are observed on the patient’s knuckles and the dorsum of his hand. No other skin or mucosal changes are noted.
A skin biopsy is performed and reveals granulomatous dermatitis with inflammatory infiltrate. What is the most probable causative organism?