A 68-year-old patient with a serious lung infection caused by Histoplasma fungus initially developed an allergic skin reaction to the standard medication itraconazole. Unable to use the typical treatment, doctors switched him to a newer antifungal drug called isavuconazole using a carefully controlled graded dose approach. The patient successfully tolerated the new medication and achieved complete resolution of his infection with sustained improvement, suggesting isavuconazole could be a viable alternative for similar patients.