A Case of Extra-Articular Coccidioidomycosis in the Knee of a Healthy Patient.

Coccidioidomycosis is a fungal infection endemic to the Southwestern United States. Extrapulmonary Coccidioides immitis infections are uncommon and occur more frequently in immunocompromised individuals. There is often a delay in diagnosis and treatment due to the chronic, indolent nature of these infections. The clinical presentation is often nonspecific, and includes joint pain, erythema, or localized swelling. Therefore, these infections may only be identified after initial treatment failure and further workup is pursued. The majority of reported cases of coccidioidomycosis involving the knee have had intra-articular involvement or extension. This report describes a rare case of peri-articular Coccidioides immitis abscess of the knee that does not communicate with the joint in a healthy patient. This case illustrates the low threshold needed for additional testing, such as fluid or tissue sampling of joint-related fluid collections if the etiology is unclear. A high index of suspicion is prudent to avoid diagnostic delay, particularly for individuals who either reside in or travel to endemic areas.