Extended report: nail disease in psoriatic arthritis--clinically important, potentially treatable and often...

To examine the relationship between the severity of nail disease and characteristics of psoriatic arthritis (PsA). We also wished to assess the clinical management of nail disease in patients with PsA.

We studied 69 patients with PsA at two visits. On the first visit, a rheumatology assessment of joint, skin and nail disease was made. On the second visit, a detailed dermatology assessment of skin and nails was made. Nail disease was analysed using a 20-nail psoriasis nail severity score (PNSS).

There were 57 (83%) patients with clinical evidence of psoriatic nail disease. Although 66 (96%) patients had been treated for skin disease, only one (1%) had received any treatment for nail disease. Severe nail disease measured by the PNSS correlated with severe skin psoriasis as indicated by the percentage of body surface area affected by psoriasis (r = 0.34, P = 0.004) and physician global assessment of psoriasis (r = 0.45, P<0.001). Patients with distal interphalangeal (DIP) joint disease had higher PNSS scores (P = 0.03). The PNSS was also associated with unremitting and progressive arthritis (P<0.001), and correlated with Stanford health assessment questionnaire (HAQ) (r = 0.34, P = 0.004), depression (r = 0.39, P<0.001) and anxiety (r = 0.34, P = 0.004) scores. Compared with dermatology assessment, the rheumatology examination of nail disease had a positive predictive value of 84% and negative predictive value of 83%.

In patients with PsA, the severity of nail disease correlates with indicators of severity of both skin and joint disease. Although rheumatologists can adequately screen for nail disease, the management of this aspect of PsA is often overlooked.