Cryptococcus neoformans tibial osteomyelitis in an immunocompetent host: a case diagnosed by tNGS.

Background: Cryptococcus neoformansis widely distributed in nature and primarily causes infections in various parts of the body through inhalation into the lungs. While C.neoformans infection predominantly occurs in immunocompromised individuals, there has been a significant increase in reports among immunocompetent hosts in recent years. Although the lungs and central nervous system constitute the most common sites of infection, cryptococcal osteomyelitis remains exceptionally rare and is typically associated with disseminated disease in immunodeficient patients. Herein, we present a rare case of isolated tibial cryptococcal osteomyelitis in an immunocompetent patient.

Case presentation: We report a case of a 64-year-old female who presented with pain, swelling, and increased local skin temperature in the left lower limb for one month without any obvious cause. The patient was initially diagnosed with osteomyelitis at a local county hospital and underwent surgical treatment. Due to poor postoperative healing, she was referred to our hospital for surgical debridement. Preoperative wound specimen culture revealed Luteimonas deserti. Simultaneously, intraoperative tissue samples were taken from the patient for targeted next-generation sequencing (tNGS) testing, which revealed the presence of C. neoformans. While the culture was negative, the C. neoformans capsular antigen test was positive. The patient had normal immune function and no underlying diseases. Ultimately, the patient was treated with fluconazole and surgery, resulting in a good prognosis.

Conclusions: we report a case of tibial osteomyelitis caused by Cryptococcus neoformans in an immunocompetent patient, with diagnosis confirmed through targeted next-generation sequencing (tNGS) and serum Cryptococcal capsular antigen testingOur results demonstrate the great potential of tNGS in the detection of infectious pathogens. In patients with negative culture results, tNGS can quickly detect various pathogens, providing accurate diagnosis and facilitating appropriate treatment for patients.