A Colombian patient living in Spain developed a serious fungal infection (histoplasmosis) that spread throughout his body and affected his bone marrow, which was discovered during his HIV diagnosis. Doctors identified the infection by examining bone marrow cells under a microscope and confirmed it with fungal culture and genetic testing. The patient was treated with antifungal medication (liposomal amphotericin B) along with HIV medications and recovered well, highlighting the importance of bone marrow testing in severely immunocompromised HIV patients.