The immune-disease angle surfaced when doctors noticed that cancer patients who also had psoriasis found their skin improved when they took the immune suppressants methotrexate (for cancer) and cyclosporine (for organ transplants).

FORBES: Skin Deep

In fact, most analysts think Enbrel, the leader in the rheumatoid-arthritis space, will also lead in psoriasis.

FORBES: Genentech And Xoma Fumble, Recover

Immunex (nasdaq: IMNX - news - people ) comes with a gem of a drug: Enbrel, a treatment for rheumatoid arthritis that may also treat other conditions, including psoriasis.

FORBES: Amgen, Immunex: The Arthritis Merger

High levels of TNF also are found in the skin of psoriasis patients.

FORBES: Chemical Chameleon

Amgen also sells Enbrel, a treatment for rheumatoid arthritis and psoriasis, and it has a handful of promising new drugs in its pipeline.

FORBES: Magazine Article

Private companies have also combed the data to find genes that play roles in diabetes, asthma, psoriasis and migraines.

BBC: What the genome can do for you

Also, Biogen faces heavy competition with two of its big drugs: Avonex (multiple sclerosis) and Amevive (psoriasis).

FORBES