New insights in occult psoriatic arthritis

Since the 1970s, asymptomatic involvement of several musculoskeletal structures was described in patients with psoriatic arthritis (PsA). We recently designated this clinical condition as occult PsA. This concept addresses an "underground" inflammatory process that can eventually cause structural damage. The percentage of PsA cases occurring in an occult manner remains to be determined but it does not seem small. From a teaching perspective, we suggest differentiating occult PsA into 3 subsets: real occult PsA, characterized by a continuous asymptomatic course; temporary occult PsA, in which the clinical course remains asymptomatic for a period; and limited occult PsA, which occurs asymptomatically in some areas of the body but is clinically evident in others. Some serum biomarkers could identify patients to be studied with imaging techniques to discover real occult PsA. Since an asymptomatic course was also reported for other spondyloarthropathies, the concept of occult arthritis could be expanded to the whole field of such conditions.