To investigate the risk factors, clinical characteristics, management, and outcomes of musculoskeletal fungal infection in Thai patients, patients aged ≥18 years definitively diagnosed with musculoskeletal fungal infection by culture and/or histopathology at Siriraj Hospital (Bangkok, Thailand) during 2002–2020 were retrospectively enrolled. Twenty-eight patients (median age: 58.5 years [range: 22–81], 57.1% male) with fungal osteomyelitis (n = 22), septic arthritis (n = 1), or fungal osteomyelitis with septic arthritis (n = 5) were included. Immunocompromised status was common (82%). Most patients had de novo infection from hematogenous spreading that usually presented at a single, non-contiguous site. The median symptom duration prior to diagnosis was 2 months. The tibia and knee were the most common site of osteomyelitis (30%) and septic arthritis (72%), respectively. The most common pathogens were Talaromyces marneffei and Cryptococcus neoformans. Organism identification from tissues at the affected sites was required in all cases. Most patients (82%) required combination surgery and systemic antifungal therapy. Among those with complete follow-up (23/28), 61% and 39% had complete and partial responses, respectively. Musculoskeletal fungal infection is an uncommon disease with insidious onset and non-specific manifestations that requires pathogen identification via tissue cultures and histopathologic studies. Combination surgery and systemic antifungal therapy yielded generally favorable outcomes.

A previously healthy 53-year-old Thai man living in central Thailand (Pathum Thani) presented with progressive swelling of his left index finger for 4 months. He worked at an advertising company, and his hobbies included gardening and decorating corals at his home. The swelling site was located where he had been bitten by an ant

T he patient's pus stain showed unstained organisms in the Gram stain (see Fig. 1C in the photo quiz), which were positive by acid-fast staining (see Fig. 1D in the photo quiz). Tissue and pus specimens were cultured at 32°C by inoculating the sediment on LJ solid medium and in a mycobacterial growth indicator tube (MGIT) (Becton, Dickinson, Sparks, MD). The cultures grew acid-fast bacilli (AFB) after 4 weeks for the pus specimen and 8 weeks for the tissue specimen. Two groups of mycobacterial colonies were identified. The first group (at 4 weeks) contained colonies that were creamy in color and turned yellow when exposed to light (photochromogenic), while the second group of colonies (at 8 weeks) appeared yellow and rough, with a welldemarcated edge. The organisms were later identified as Mycobacterium marinum and M. ulcerans, respectively (1). DNA extracted from pus and tissue samples were evaluated by PCR targeting the 16S rRNA gene and by the IS2404 insertion elements. PCR targeting the 16S rRNA gene confirmed Mycobacterium species most closely matching M. marinum and/or M. ulcerans. The sequences of the IS2404 amplicon were identical to those from M. ulcerans. Coinfections due to M. marinum and M. ulcerans, thus, were diagnosed based on cultures (M. marinum and M. ulcerans) and PCR primers specific for M. ulcerans. M. marinum and M. ulcerans were subjected to antimicrobial susceptibility testing (AST) using a broth microdilution susceptibility test (2), and both organisms were susceptible to clarithromycin, doxycycline, moxifloxacin, and rifampin. The patient was empirically treated with rifampin, clarithromycin, and streptomycin together with multiple surgical debridements of his left index finger, which resulted in a significant reduction of the inflammation and resolution of the abscess. Nontuberculous mycobacteria (NTM) are widely distributed in the environment, with high isolation rates worldwide. These organisms can be found in soil and water, including both natural and treated water sources. The most common clinical manifestation of NTM disease is lung disease, but lymphatic, skin and soft tissue, and disseminated diseases are also frequently described. M. marinum is the cause of "swimming pool granuloma" or "fish tank granuloma." A systematic search of the literature found that exposure to a fish tank in a household with indoor or outdoor aquariums, death of the tank fishes, and injury from or contact with a fish spine or oysters were commonly identified risk factors (3). Infection is typically acquired from a soft tissue injury to the hand in an aquatic environment, usually without a history of direct contact with fish. M. ulcerans is widely dispersed in geographic areas in the watersheds of tropical rain forests, primarily in Africa, Southeast Asia, Australia, and South and Central America (4, 5). M. ulcerans causes indolent, progressive necrotic lesions of the skin and

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