Primary Cutaneous Cryptococcosis Mimicking Vasculitis in a Patient with Rheumatoid Arthritis.

Opportunistic infections caused by Cryptococcus spp. are well-documented among people with HIV. However, the incidence of cryptococcosis has also recently risen among other immunocompromised patients. Here, we reported a rare case of primary cutaneous cryptococcosis in a 73-year-old man who had been taking corticosteroids long-term for rheumatoid arthritis (RA). Despite receiving antimicrobial treatment, he developed painful, non-healing ulceronecrotic lesions accompanied by haemorrhagic bullae on his right forearm and upper arm. Initially, it was thought that the patient had RA-associated vasculitis. A skin biopsy showed numerous small round structures that were stained with periodic acid-Schiff in the dermis. The wall of round structures had positive mucicarmine stain, consistent with the presence of mucopolysaccharides capsule of yeast. Also, the cryptococcal antigen test was positive in the serum. On the 14th day of fluconazole treatment, there was an improvement in the clinical picture, including a reduction in pain. However, he died from complications arising from his pre-existing systemic disease, specifically heart failure. This case highlights the importance of considering cutaneous fungal infections in immunocompromised patients with non-healing skin lesions despite antimicrobial treatment.