Etretinate (trade name Tegison) is a medication developed by Hoffmann–La Roche that was approved by the FDA in 1986 to treat severe psoriasis. It is a second-generation retinoid. It was subsequently removed from the Canadian market in 1996 and the United States market in 1998 due to the high risk of birth defects. Etretinate remains on the market in Japan as Tigason. The mechanism of action of etretinate is still incompletely understood although, like retinoic acid, it is thought to interfere with the terminal differentiation of keratinocytes. Etretinate activates retinoid receptors, causing an induction of cell differentiation, inhibition of cell proliferation, and inhibition of tissue infiltration by inflammatory cells.