[The role of hereditary factors in the development of psoriatic arthritis and the nature of its interrelations with psoriasis].

Altogether 83 families of probands with psoriatic arthritis and the same number of families of probands with common skin psoriasis were investigated in order to study the role of hereditary factors in the development of psoriatic arthritis and the type of its interrelationship with psoriasis. Obvious accumulation of repeated cases of this disease was observed among the probands' relatives. Genetic analysis made it possible to reject the monogenic type of inheritance of psoriatic arthritis and to prove the multifactorial nature of its inheritance confirmed in 68%. Analysis of the distribution of repeated cases of psoriatic arthritis and uncomplicated psoriasis in both types of families helped to determine a genetic correlation coefficient (0.93) indicating great similarity of the genetic systems of both types of diseases therefore they could be regarded as the clinical variants of one disease--psoriasis.