A 13-year-old boy developed a serious fungal infection of his heart valve after receiving an artificial valve replacement. The initial antibiotic (itraconazole) did not work because the fungus became resistant, likely by forming a protective biofilm. After identifying the resistant fungus through specialized testing, doctors switched to a different medication called caspofungin. The patient fully recovered with this new treatment and remained healthy during follow-up, showing that combination of precise identification and targeted treatment can overcome antibiotic resistance.