CNS histoplasmosis coexisting with pulmonary tuberculosis in a HIV negative patient: case report.

Background: Tuberculosis is a highly prevalent disease in India, while Histoplasmosis, an emerging disease, is often underreported due to limited resources in developing countries. Coinfection with both these organisms is rarely documented in immunocompetent host. Due to overlapping symptoms, it can be easily missed and treatment delays are not uncommon.

Case presentation: Here, we report a case of a 62-year-old male with a chronic history of intermittent fever and dry cough, splenomegaly, lymphadenopathy, and persistent pancytopenia. He was diagnosed with tuberculosis with cartridge-based nucleic acid amplification test (CBNAAT) positivity from a paratracheal lymph node biopsy. Simultaneously, a bone marrow biopsy revealed Histoplasmosis and the patient was started on dual treatment (Itraconazole and antitubercular drugs). After an initial response, the patient developed new space-occupying cerebral lesions. CSF histoplasma antigen was also positive. The reason for treatment failure was likely to be drug interaction (suboptimal levels of itraconazole due to rifampicin). The patient received liposomal amphotericin and subsequently put on a modified antitubercular treatment regimen to avoid interaction with itraconazole. At 2-month follow-up, the patient's condition significantly improved with a substantial resolution in CNS lesions.

Conclusions: Histoplasmosis and tuberculosis have overlapping symptoms, diagnosing one does not preclude the possibility of other, even in non-HIV patients. Clinicians should also be vigilant about potential drug interactions.