Histocompatibility studies in psoriasis vulgaris: family studies.

: A significant correlation between certain histocompatibility antigens, psoriasis and psoriatic arthritis is well established. Familial studies of psoriatic patients have shown a familial aggregation of psoriasis and psoriatic arthritis. In the present investigation, we studied 2 families in which psoriasis and/or psoriatic arthritis were seen in several members of different generations. HLA typing and mixed lymphocyte culture studies were performed. The results provide further documentation of the complexity of the genetic influences in psoriatic arthritis and psoriasis.