Role for familiarity and genetic features in the therapeutic response of psoriatic arthritis

Aim of the study: To analyze PsA patients with and without a familiar distribution for Ps and PsA, in order to better evaluate the genetic data, to verify the existence of different expression of the disease and finally to define the susceptibility to treatment in these patients. Materials and methods: 230 PsA patients were selected for familiar or sporadic distribution of the disease and were evaluated for the main clinical, demographic, radiological and laboratory features, as well as for the ongoing treatments. In each patient HLA class I (A,B,C) and II (DRB1, DQB1) antigens were typed with PCR-SSP method while MICA-A exon 5 microsatellite typing was performed by heteroduplex analysis in 122 subjects. Results: A familiar distribution for Ps and PsA was found in 68 patients (29.6%) although only two patients had familiarity for PsA. In the familiar PsA group the male prevalence was significantly higher respect to the sporadic one (p<0.001) and the more frequently involved relative was the father (28%). Mean age (p<0.006) and age at onset of Ps (p<0.004) and PsA (p<0.014) were significantly lower in familiar respect to sporadic PsA. Between the two groups no difference was found concerning the articular involvement, the radiological findings, the disease activity (including n° of painful/swollen joints), the inflammatory laboratory parameters (including ESR and CRP) and genetic aspects, incuding the frequencies of MICA-A alleles that were analysed in 30 patients with the familiar form and in 92 with the sporadic one. In the follow-up the therapeutic response to any evaluated treatment adopted for PsA did not show any significant difference in the two groups. All these results were confirmed even when the patients in the two groups were matchable for sex, age and disease duration. Conclusion: Our results confirm that familiar PsA is characterized by an early onset of the disease and by a male and fatherly predominance respect to the sporadic form, although the clinical-radiologic findings, the genetic typing and the therapeutic response do not permit us to identify any particular subset.