The Social Security Administration recognizes autoimmune disorders in their Bluebook under Section 14 so if it has impacted your ability to work you may qualify.
If you have PSa you may qualify for Social Security disability. People with psoriatic arthritis may qualify under dysfunction of a joint or inflammatory arthritis.
Psoriasis is not specifically listed by the SSA but a person may qualify for disability if the psoriasis does not respond to treatment in three months. Call 512-454-4000