RESUMEN
Introduction: Coccidioides immitis is a fungus that develops in endemic areas characterized by dry climates, with little rainfall and easy aerial dissemination. The most common form of infection is pulmonary coccidioidomycosis, although it is often asymptomatic. There are non-respiratory forms of this disease. Osteomyelitis is an extrapulmonary manifestation of C. immitis infection. Symptoms are usually nonspecific and radiographic findings are often confused with bone tumors. Treatment of coccidioidal osteomyelitis is often challenging. Case Presentation: We report a case of a 3-year-old preschool girl from an endemic area for coccidioidomycosis who presented with pain and swelling on her left ankle. Initially, antibiotic treatment is administered for a suspected insect bite. However, her symptoms worsened and X-rays showed a lytic-like lesión. She was admitted to the hospital for biopsy and drainage surgery. The histopathological study confirms coccidioidomycosis osteomyelitis. She was started on long-term anti-fungal treatment. At 6-month follow-up, symptoms and signs of infection have been solved and X-ray image shows evidence of bone healing. Conclusion: It is important to take into account aspects related to exposure to this fungus, such as the patient's place of residence and recent trips so that the diagnostic and therapeutic approach is appropriate. Coccidioidal osteomyelitis is an infrequent pathology, especially in patients without other comorbidities. Treatment is complex and often requires not only antifungal drugs but also surgical debridement.