Multisystemic Imaging Features of Coccidioidomycosis

Coccidioidomycosis, a disease induced by the dimorphic fungi Coccidioides immitis and Coccidioides posadasii, is endemic to the southwestern United States and occurs with a myriad of clinical and imaging manifestations, which range from limited pulmonary disease to disseminated multiorgan infections. Humans are infected when arthroconidia in the soil are disturbed and dispersed into the air. Once inhaled, arthroconidia form spherules, which trigger a host cell-mediated immune response. If this response is adequate, it results in granuloma formation, halting the infection. However, an insufficient response leads to morphologic conversion into endospores that are capable of hematogenous and lymphatic dissemination to other organ systems. Given the airborne route of transmission, there is a propensity for pulmonary infections, which represent the most common disease manifestation of coccidioidomycosis. CT features of pulmonary involvement include nodules, lobar or segmental consolidation, and multifocal consolidation in the acute phase, which can occur with mediastinal adenopathy and/or pleural effusions. Extrapulmonary dissemination is rare, occurring in 1%-5% of patients. Musculoskeletal involvement is common in cases of dissemination, with discitis-osteomyelitis being a frequent manifestation, often demonstrating relative disk sparing analogous to that seen with tuberculosis or other causes of atypical infectious spondylitis. When osteomyelitis of the appendicular skeleton is juxta-articular, it can progress to septic arthritis, with fungal tenosynovitis and soft-tissue abscesses being less common musculoskeletal features. Neurologic involvement is frequent, with complications including meningitis, cerebritis, and abscess formation, which can induce vasculopathic and neuropathic sequelae, leading causes of morbidity and mortality in cases of dissemination. Other systems are less commonly involved, but conditions include pyelonephritis, peritonitis, lymphadenitis, and endocarditis. ^©RSNA, 2026 Supplemental material is available for this article.