Surgical pathology of skeletal coccidioidomycosis: a clinical and histopathologic analysis of 25 cases.

Skeletal coccidioidomycosis is a rare complication of pulmonary coccidioidomycosis that remains incompletely characterized, and its histopathologic features have not been systematically evaluated. All skeletal coccidioidal infections (2000 to 2012) were retrieved from the University of Arizona and Mayo Clinic in Arizona pathology archives. Clinical history and histologic features were reviewed. Among 25 patients (median age 40 y; 17 men), infections involved bones (2 cases), joints (6), or both (17), usually in the distal extremities (68%), especially the wrist (32%). History included previously documented coccidioidomycosis (13), autoimmune disease (8), diabetes (6), malignancy (4), and iatrogenic immunosuppression (10). Common symptoms (median 3 mo) included pain/arthralgia (21) and swelling (10). Cultures and serology were positive in 15 of 17 (88%) and 19 of 22 patients (86%), respectively. Treatment included surgical debridement(s) and chronic antifungal medication(s). Histologic review showed granulomas in all cases, ranging from poorly to well formed, with or without necrosis. Spherule density varied widely (mean 4.8/HPF; range <0.1 to 13.5/HPF). Composition of inflammatory infiltrates, degree of necrosis, and extent of fibrosis did not significantly differ between immunocompetent and immunocompromised patients. Eosinophils were only seen in one third of cases; when present, eosinophils were almost always rare. 10 patients experienced recurrent infection, 8 of whom were immunocompromised; the remaining patients recovered. In conclusion, distal extremities are the most common sites of skeletal coccidioidomycosis encountered by surgical pathologists. This condition is strongly associated with autoimmune disorders and immunosuppression. Spherules are sometimes rare, and multiple modalities including serology, culture, and histology may be required for diagnosis.