Cryptococcosis in a seemingly immunocompetent patient presenting with knee and lower limb soft tissue infection complicated by meningitis: a case report

Cryptococcus neoformans typically causes pulmonary or central nervous system (CNS) infections. However, osteoarticular manifestations, particularly as the initial presentation, are rare, especially in immunocompetent hosts. We report the case of a 65-year-old apparently immunocompetent woman admitted for generalized pain following a fall. Ten days post-admission, she developed fever and rapidly progressing soft tissue swelling in the right lower limb and knee. Despite the absence of overt immunodeficiency, the infection disseminated, leading to meningitis. Diagnosis was confirmed via fungal culture of lower limb secretions and metagenomic next-generation sequencing (mNGS) of knee joint tissue. Despite aggressive antifungal therapy, the patient's condition deteriorated, resulting in a fatal outcome. This case underscores the diagnostic challenge of cryptococcal osteoarticular infections in immunocompetent individuals. It highlights the utility of mNGS in diagnosing culture-negative infections and serves as a reminder that cryptococcosis should be considered in the differential diagnosis of fever of unknown origin with musculoskeletal involvement, even in the absence of traditional risk factors.