The many faces of psoriatic arthritis: their genetic determinism.

In this review, we propose a model of PsA as a complex genetically determined autoimmune-mediated disease having a heterogeneous variety of subphenotypes, with each subphenotype under the control of a different susceptibility-associated HLA allele. Since the specific HLA molecules encoded by each susceptibility allele dominantly select a T cell repertoire with the property of recognizing different peptides, we hypothesize each subphenotype reflects a distinct adaptive autoimmune response directed to different target molecules that is mediated by T cells within each selected repertoire. The interaction among the patients' susceptibility alleles in the selection of their T cell repertoires determines a spectrum of overall clinical disease severity, varying from mild to severe. We further speculate that these different immune responses may result in activation of different immune effector pathways, which might therefore respond differently to various specific biologic agents.