Syndrome of inappropriate antidiuretic hormone release secondary to central nervous system coccidioidomycosis with vasculitis.

A man in his 60s presented to the clinic due to night sweats and weight loss following pneumonia. He was found to have hyponatraemia due to a syndrome of inappropriate antidiuretic hormone (SIADH). CT of the thorax was concerning for pulmonary nodules. He was ultimately diagnosed with pulmonary coccidioidomycosis (CM) and started on fluconazole 400 mg daily with improvement in symptoms. Due to the report of headaches, head MRI was conducted which suggested central nervous system (CNS) involvement. Cerebrospinal fluid analysis was consistent with CNS CM and head magnetic resonance angiography confirmed the presence of CNS vasculitis. Fluconazole dose was increased to 800 mg daily which the patient continued to tolerate and showed improvement. This report depicts a case of SIADH associated with CNS CM with vasculitis and demonstrates the importance of high clinical suspicion for SIADH secondary to CNS CM in the setting of hyponatraemia and headache.