Comparison of clinical and immunogenetic features in familial versus sporadic psoriatic arthritis

Objective To compare patients with familial versus sporadic psoriatic arthr itis (PsA) with respect to clinical, radiological and immunogenetic feature s. Methods All patients were identified from the University of Tor-onto Psoria tic Arthritis Clinic. Familial and sporadic PsA were distinguished based on the proband's self-reported history. The probands were compared at present ation to clinic with respect to demographic information age of onset of pso riasis and inflammatory arthritis, disease activity disease damage, laborat ory variables, functional class and HLA antigens. The two groups were compa red rising a univariate analysis. Results In total 407 patients were included. Thirty-six patients (8.8%) wer e eliminated as they reported a family history of arthritis in the absence of psoriasis. Of the remaining 371 patients, 150 patients reported a positi ve family of either PsA or psoriasis. 221 patients (54.2%) had no family hi story of psoriatic arthritis, psoriasis, or "arthritis". The familial group were younger. at presentation to clinic (p = 0.003), had an earlier age of onset of psoriasis (p = 0.001) and inflammatory arthritis (p = 0.001) and were more likely to be receiving treatment (p = 0.001). The mean number of actively inflamed joints was higher in the sporadic group (p = 0.035), alon g with a higher frequency of rheumatoid factor positivity (p = 0.04). Only the age of onset variables and medication use retained significance after c orrection for multiple comparisons. Conclusions In comparing probands with familial versus sporadic PsA, we not ed a marked difference in the age of onset of psoriasis and inflammatory ar thritis, along with other differences ill several clinical variables. These differences may be helpful in identifying PsA patients with a stronger gen etic predisposition.