A rare case of sporotrichosis in a patient with late latent syphilis and diabetes mellitus: immunological aspects of sporotrichosis.

Sporotrichosis, caused by Sporothrix schenckii, typically infects humans through skin trauma, leading to nodules or ulcers that complicate diagnosis. Rare forms, such as disseminated cutaneous sporotrichosis, occur more often in immunosuppressed patients or those with diabetes or alcohol use disorder. We report a 49-year-old male patient with type 2 diabetes mellitus who developed painful ulcerations on his lower limbs following a cat scratch. A deep tissue biopsy confirmed mycelial hyphae, and culture identified Sporothrix spp. A biopsy from a left thigh lesion revealed syphilitic exanthem findings. Treponema pallidum antibodies were positive, with a TPHA titer of 1 : 320. The patient was diagnosed with sporotrichosis and late latent syphilis, treated with benzathine penicillin for syphilis and itraconazole for sporotrichosis, resulting in significant improvement after two months. This case underscores the importance of mycological diagnostics - deep tissue biopsy, culture, and histopathological analysis - in distinguishing sporotrichosis from similar conditions, especially in immunocompromised patients with unresponsive lesions.