The accessory pulleys linked to the flexor tendons are thicker in patients with psoriatic arthritis (PsA), even in individuals with minimal disease activity, and particularly in individuals with a history of tenosynovitis and dactylitis, according to the results of an exploratory study published in the Annals of the Rheumatic Diseases. The results lend support to a deep Koebner response in these individuals.
The researchers sought to explore whether the accessory pulleys were thickened in patients with PsA, thus exhibiting the Koebner response, in which injury or trauma to the skin causes further formation of psoriasis plaques. A total of 96 patients were enrolled in the study (27 with PsA, 27 with rheumatoid arthritis [RA], 23 with psoriasis, and 19 healthy control patients).
The A1, A2, and A4 pulley thickness was calculated with a high-resolution probe. All the patients evaluated were in remission or had low disease activity, and current dactylitis was excluded. Within a total of 864 pulleys investigated, participants with PsA had significantly thicker pulleys in every digit compared with participants with RA (P <.001 and P =.003) and with healthy control patients (P <.001).
Patients in the RA and psoriasis groups had some pulleys in some digits that were thicker than those of healthy control patients. In addition, the second digit A1 pulley thickness was higher in patients with PsA and prior dactylitis (P =.020).
There were more pulleys that were thickened in the PsA group (68%) than in the RA group (17%; P <.001), and in the healthy control patients (7.6%; P <.001).
The investigators concluded that in patients with established PsA, accessory pulleys are thickened compared with those with RA, psoriasis, and healthy control patients, which is especially true in patients with a history of dactylitis. This supports the idea of deep Koebnerization in dactylitis and in sites with high physical stress, which is suggestive of tissue damage, rather than inflammation, in these patients.
Tinazzi I, McGonagle D, Aydin SZ, Chessa D, Marchetta A, Macchioni P. ‘Deep Koebner’ phenomenon of the flexor tendon-associated accessory pulleys as a novel factor in tenosynovitis and dactylitis in psoriatic arthritis [published online March 6, 2018]. Ann Rheum Dis. doi: 10.1136/annrheumdis-2017-212681