Sayyiduna Ali (may Allah be pleased with him) said: Whoever marries a woman who has vitiligo, insanity, leprosy or qarn, the husband has the choice as long as he has not had intercourse with her: if he wishes he may keep her, and if he wishes he may divorce her. And if he has had intercourse with her, then in return for that he must pay her the dowry.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14229