Psoriasis and arthritic lesions in relation to the inheritance of HLA genotypes: a family study.

This family consists of forty-eight subjects, all of whom have been examined with regard to the presence of psoriasis and nearly all for the presence of arthritic lesions (sacroiliitis and peripheral arthritis). All the members have been tissue-typed not only for HLA-A, B and C locus products but also for D locus products. This has enabled us to study the entire HLA chromosomal region. In the family concerned we have found that those subjects haploidentical with the proband have, to a very large degree, either one or all clinical manifestations, which demonstrates a close genetic relationship between joint (especially sacroiliitis) and cutaneous manifestations. These findings prompt us to repeat our previously made proposal about different phenotypic expressions of the same genotype. In this family study the disease-associated haplotypes did not contain the genes for B13, 17 or 37 antigens which are known to occur frequently in psoriatic patients. However, not all psoriasis patients have these antigens. Despite that, we believe that the gene(s) which increase the likelihood of developing psoriasis are identical in all patients and therefore family studies where the proband does not carry the particular psoriasis associated B-alleles are equally illuminating as to the inheritance pattern of disease.