Tretinoin is the acid form of vitamin A and so 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 (brand names Aberela, Renova, Retin-A, Avita). Tretinoin is most commonly used as a form of acne treatment. It was the first retinoid developed for this type of topical use. Tretinoin is the best studied retinoid in the treatment of photoaging. ITopical tretinoin is also used to treat and reduce the appearance of stretch marks by increasing collagen production in the dermis.

Tretinoin t is also used to treat acute promyelocytic leukemia (APML) which is sold for this indication by Roche under the brand name Vesanoid. Its success in treating acute promyelocytic leukemia was a major breakthrough in the treatment of this type of leukemia. It works in APML because the majority of cases involve a chromosomal translocation of chromosomes 15 and 17, which causes genetic fusion of the retinoic acid receptor (RAR) gene to the promyelocytic leukemia (PML) gene. This fusion PML-RAR protein is responsible for preventing immature myeloid cells from differentiating into more mature cells. This block in differentiation is thought to cause leukemia. ATRA acts on PML-RAR to lift this block, causing the immature promyelocytes to differentiate to normal mature blood cells.

Tretinoin is used by some as a hair loss treatment and also a component of many commercial products that are advertised as being able to slow skin aging or remove wrinkles.

Formal Chemical Name (IUPAC)
(2E,4E,6E,8E)-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-enyl)nona-2,4,6,8-tetraenoic acid

References

http://en.wikipedia.org/wiki/Tretinoin