Abstract
OBJECTIVE: To analyze whether HLA antigens may influence the age of onset of both psoriasis and psoriatic arthritis (PsA). METHODS: One hundred thirty-five patients with PsA (77 men, 58 women, mean age 47 +/- 12 yrs) were analyzed. All were studied with a standard protocol and consecutively recruited to evaluate the relative contribution of HLA-Cw and HLA-B27 alleles to PsA susceptibility. Fifty patients with psoriasis alone were also recruited to analyze the role of HLA-Cw genes on disease susceptibility. HLA-Cw antigens were investigated by DNA based methods (PCR-SSOP), while HLA-B27 antigen was studied using serological methods, and their frequencies were compared to 177 healthy controls. RESULTS: In PsA Cw6+ patients, the mean age at psoriasis onset was 23 +/- 12 years compared to 32 +/- 12 years in Cw6- patients (p = 0.012). Age of arthritis onset was 35 +/- 13 years in Cw6+ patients versus 38 +/- 12 years in Cw6- patients (p = NS). In patients with psoriasis alone, the age at onset was 18 +/- 10 years in Cw6+ versus 30 +/- 11 years in Cw6- patients (p < 0.01). Cw6 correlated well with a positive family history of psoriasis among first-degree relatives (64% of patients with family history were Cw6+, whereas only 30% of those without family history had this allele (p < 0.05). The onset age of psoriasis in HLA-B27+ patients was 24 +/- 8 years vs 32 +/- 14 years in B27- patients (p = 0.026), whereas onset age of arthritis was 30 +/- 10 years in B27+ compared to an age of onset of 40 +/- 12 in B27- patients (p = 0.0056). CONCLUSION: Our results confirm the known association between Cw6, early onset psoriasis and positive family history (type I psoriasis). The association between HLA-B27 and earlier onset ages for both psoriasis and arthritis in PsA had not previously been emphasized. The HLA antigens may determine not only disease susceptibility, but also the age of disease onset in psoriasis and PsA.
