The should compensate him for misdiagnosing him.
But they should not be held accountable for him wasting all of his money because of it, that was his own choice, and as an adult male he can not blame others for his own actions.
If Debussey killed someone because of a bad haircut, then its still Debusseys responsibility, not the hairdresser. The hairdresser = still responsible for the bad haircut.