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Foot involvement is very frequent in patients affected by psoriatic arthritis (PsA). However, evaluation of the painful foot can be problematic, because it is often difficult to distinguish between arthritis, tenosynovitis, and enthesopathy. Plain radiographs can show bone erosion or other features of joint involvement, but give little information about the soft tissues. We therefore studied foot involvement in 31 PsA patients using high resolution sonography, and compared the results with the findings on x-ray and clinical examination. Ultrasound revealed pathological findings in a large proportion of the patients, most of whom exhibited no clinical (pain or swelling) or radiological signs of foot involvement at the time of the study. Our data suggest that involvement of the tendons and entheses may be more frequent in PsA patients than has thus far been supposed, even in cases of not particularly aggressive disease, and that clinical evaluation tends to underestimate these manifestations.

Objective: To study the prevalence of hepatitis C virus (HCV) infection in 2 groups of patients, one group with psoriasis and the other with psoriatic arthritis (PsA)., Methods: We detected anti-HCV antibodies by ELISA and by a recombinant immunoblot assay (RIBA) in the sera of 50 patients with psoriasis and 50 with PsA. As controls we used a group of 76 patients with rheumatoid arthritis (RA), and referred to data on the prevalence of HCV in the general Italian population., Results: By ELISA, anti-HCV antibodies were detected in 6/50 (12%) patients with PsA, in 5/50 (10%) patients with psoriasis, and in 4/76 (5.2%) patients with RA. All the reactive PsA and RA sera also tested positive on RIBA, while only 3 of the 5 positive results for sera of patients with psoriasis were confirmed by RIBA. The prevalence of HCV infection in patients with psoriasis was not significantly higher than in controls. In contrast, the rate of HCV infection observed in the 50 patients with PsA was higher than that in the other groups, the difference being statistically significant between patients with PsA and the general population., Conclusion: Our data do not support the hypothesis that HCV infection may play a role in the pathogenesis of psoriasis. On the other hand they show a statistically significant difference between the prevalence of HCV infection in patients with PsA and the general population.

A 26-year-old male patient being treated with alpha-interferon for chronic hepatitis C developed psoriasis, seronegative oligoarthritis and sacroiliitis after four months. The close temporal relationship between the alpha-interferon therapy and the onset of skin and articular lesions strongly suggests that the drug played a role in the induction of the disease despite the absence of HLA antigens related to psoriatic arthritis. We cannot exclude the possibility that immunological alterations associated with HCV infection could have constituted a predisposing factor in the onset of the disease.