Tretinoin is the acid form of vitamin A and is also known as all-trans retinoic acid or ATRA. It is a drug commonly used to treat acne vulgaris and keratosis pilaris. It is available as a cream or gel It is also used to treat acute promyelocytic leukemia.
Its success in treating acute promyelocytic leukemia was a major breakthrough in the treatment of this type of leukemia. It works in APL because the majority of cases involve a chromosomal translocation of chromosomes 15 and 17, which causes genetic fusion of the retinoic acid receptor gene to the promyelocytic leukemia gene.