Voriconazole-Induced Periostitis: A Mimicker of Skeletal Coccidioidomycosis

Objective: Challenging differential diagnosis Background: Coccidioidomycosis is caused by the fungi Coccidioides immitis and Coccidioides posadasii, which are endemic to the southwestern United States and other countries of the Western Hemisphere. Pulmonary coccidioidomycosis is the most common form of coccidioidomycosis. Rarely, coccidioidal infection disseminates to meninges, bones, skin, and soft tissues. While fluconazole remains the first line of treatment and is used for most patients, voriconazole is used in selected refractory cases of coccidioidomycosis. Voriconazole has more fluorine molecules than other azoles, and over time the fluorine molecules in voriconazole can cause disorganized bone formation in the periosteal region (periostitis), causing generalized bony pain, and radiographically can mimic skeletal coccidioidomycosis. While voriconazole-induced periostitis has been noted in aspergillosis and other infections, it has not been reported commonly in patients with coccidioidomycosis. Case Report: We present a case of a 50-year-old female patient with a diagnosis coccidioidal meningitis who was refractory to fluconazole and was treated with voriconazole. She presented with bony pain, which was initially radiographically attributed to multifocal skeletal coccidioidal infection. Reflecting upon the patient's history and serum levels of fluoride and bone alkaline phosphatase, a diagnosis of voriconazole-induced periostitis was made. Discontinuation of the voriconazole resulted in resolution of the periostitis. Conclusions: Voriconazole-induced periostitis should be considered in patients with musculoskeletal pain with a history of voriconazole treatment or with laboratory abnormalities, such as elevated fluoride levels and/or bone alkaline phosphatase. Discontinuation of voriconazole reverses the condition promptly.