In 1905, pathologist Samuel Darling described in Panama a pathogen resembling the amastigote form of Leishmania spp., responsible for granulomatous lesions in the lungs, liver, spleen, and bone marrow. This microorganism, later named Histoplasma capsulatum , remains a diagnostic challenge, especially in immunosuppressed patients such as those living with HIV/AIDS. A 63-year-old man from Piraju (SP) presented to a referral hospital with anorexia, weakness, abdominal pain, diarrhea, and 10-kg weight loss over three months. He also reported dry cough and night sweats for one month. Initial investigation led to an HIV diagnosis. Additional tests included upper endoscopy (showing oral-esophageal candidiasis) and colonoscopy with biopsy, whose external pathology report suggested intestinal leishmaniasis. He was admitted for treatment of the diagnosed conditions and investigation of other opportunistic infections, such as Cryptococcus neoformans , tuberculosis, and cytomegalovirus. Pulmonary evaluation included bronchoscopy and bronchoalveolar lavage; biopsy revealed vacuolated macrophages filled with numerous budding yeasts, characteristic of pulmonary histoplasmosis. Due to histopathological similarity between Histoplasma and Leishmania , the colon biopsy slides were re-evaluated by the institutional pathology service, confirming intestinal histoplasmosis. Thus, the diagnosis was disseminated histoplasmosis, requiring adjustment of amphotericin B dosing and treatment duration. The patient improved clinically and laboratorially, allowing ART initiation and hospital discharge. This case illustrates the diagnostic challenges in immunosuppressed patients, especially those with AIDS, in whom multiple opportunistic infections may coexist and mimic other conditions. The morphological similarity between Histoplasma and Leishmania can lead to misdiagnosis, negatively impacting treatment. More than a century after its discovery, accurate diagnosis of Histoplasma capsulatum remains crucial to avoid inadequate therapeutic approaches.
Duarte et al. (Sun,) studied this question.