As nouns the difference between lupus and psoriasis

is that lupus is any of a number of autoimmune diseases, the most common of which is systemic lupus erythematosus while psoriasis is a noncontagious disease whose main symptom is gray or silvery flaky patches on the skin which are red and inflamed underneath when scratched.

As a proper noun Lupus

is a summer constellation of the northern sky, said to resemble a wolf. It lies south of the constellation Libra.