Distal extremity swelling with pitting edema in psoriatic arthritis: a case-control study

To evaluate the frequency and the clinical characteristics of distal extremity swelling with pitting edema in patients with psoriatic arthritis (PsA).

This was a case-control study of consecutive outpatients with PsA (old and new diagnosis) observed over a 3-month period in three secondary referral centers in Italy. As controls we used the two consecutive rheumatic outpatients, excluding those with spondylarthropathies, observed after a PsA patient. The demographic and clinical features were assessed by clinical examination and review of the medical records.

A total of 183 patients with PsA and 366 controls were evaluated. Distal extremity swelling with pitting edema was recorded in 39/183 (21%) PsA patients and in 18/366 (4.9%) controls (p < 0.0001). In 8/39 (20%) patients this feature presented as a first, isolated manifestation of PsA, and in 8 others it was associated with other features of PsA at diagnosis. The upper and lower extremities were affected, predominantly asymmetrically, in 40% and 60% of the cases respectively. In patients with pitting edema compared to those without this feature, the frequency of Achilles enthesitis and plantar fasciitis, calculated together, was higher (p < 0.05) and the duration of arthritis was significantly lower (p = 0.02). In 7 patients the clinical evidence of a predominant involvement of tenosynovial structures was confirmed by MRI.

Upper or lower distal extremity swelling with pitting edema due to tenosynovitis, usually unilateral, is a common feature in PsA patients and may represent the first, isolated manifestation of the disease.