Isolated Central Nervous System Histoplasmosis Presenting With Ischemic Pontine Stroke and Meningitis in an Immune-Competent Patient

Importance: Histoplasmosis, a systemic mycosis caused by the fungus Histoplasma capsulatum, primarily affects immune-suppressed patients and commonly involves the lung and rarely the central nervous system (CNS). Herein, we report a case of isolated CNS histoplasmosis presenting with pontine stroke and meningitis. Observations: A 35-year-old, white, immune-competent man was transferred from an outside facility with worsening dysarthria and confusion after having presented 4 weeks prior with dysarthria, gait ataxia, and bilateral upper extremity weakness. Brain magnetic resonance imaging revealed bilateral pontine strokes, and the working diagnosis was ischemic infarctions, presumed secondary to small vessel vasculitis. Cerebral spinal fluid (CSF) examination showed marked abnormalities including an elevated protein level (320 mg/dL), low glucose level (2 mg/dL), and high white blood cell count (330/mm(3); 28% lymphocytes, 56% neutrophils, and 16% monocytes) suggestive of a bacterial, fungal, or tuberculosis meningitis. Empirical antibiotics and a second trial of intravenous steroids were started before infectious etiologies of meningitis were ultimately ruled out. Repeated magnetic resonance imaging of the brain revealed no evidence of new ischemic lesions. On hospital day 11, results of his CSF Histoplasma antigen and urine antigen tests were positive. His CSF culture also was positive for H capsulatum. The patient was treated initially with liposomal amphotericin B, 430 mg daily, but changed to voriconazole, 300 mg twice daily, secondary to renal insufficiency and eventually continued treatment with itraconazole cyclodextrin, 100 mg twice daily. Computed tomographic imaging revealed obstructive hydrocephalus, and a ventriculoperitoneal shunt was placed that successfully decompressed the ventricles. At 1 year, the patient demonstrated good clinical improvement and results of follow-up CSF cultures were negative. Conclusions and Relevance: While pulmonary involvement of histoplasmosis in immune-suppressed patients is common, systemic presentation of this fungal infection in immune-competent patients is rare and self-limiting. Isolated CNS histoplasmosis is exceedingly rare. Clinicians should consider CNS histoplasmosis in the differential diagnosis in atypical stroke cases, particularly those presenting with meningitis.