Background PsA can be difficult to distinguish from osteoarthritis (OA) and the treatments vary greatly. Nail involvement can occur in about 15–50% patients with psoriasis1, which may aid differentiation from OA. If US can reliably detect nail bed changes in early disease then it might be helpful in differentiating PsA from OA
Objectives This study aims to investigate the nail bed changes seen in patients with PsA and OA using US and MRI, and to determine the impact of nail bed changes on quality of life (QOL).
Methods Patients who fulfilled the CASPAR PsA or 1990 ACR OA classification criteria were recruited. At baseline, clinical assessment included patient and physician's visual analogue scale (VAS), tender and swollen joints, patient's Leeds Enthesitis Index and quality of life specific to nail psoriasis (NPQ10). Nail abnormalities on the dominant hand such as onycholysis, pitting, nail bed hyperkeratosis and nail bed crumbling were documented. Using US, each nail (1–5) was scored dichotomously for pitting/irregularity, loss of normal trilaminar appearance of the nail. Each nail was scored semi quantitatively for power doppler (PD) signal (0–3) in the nail bed, nail matrix and dermis, and assigned a total PD score. All patients had an MRI of the dominant 2nd to 5th finger.
Results 14 patients were recruited; demographics, clinical and US detected nail changes are documented in Table 1. Clinical nail changes were not seen in the OA group, but were relatively common in the PsA group. In the PsA group, 54% of nails had US detected structural abnormalities; 12% pitting and 52% loss of trilaminar layer. Only 20% of OA nails had US detected abnormalities. There was a strong relationship between the presence of clinical nail change and US structural changes (chi square 10.769 df 1 p=0.001) but not PD signal score. There was no relationship between clinical or US detected nail scores and NPQ10, patient or physician VAS, swollen joint count or Leeds Enthesitis Index. MRI analysis is pending.
Conclusions In this small prospective study, structural abnormalities detected by US appear to correlate well against clinical structural findings, but PD signal does not. No relationship was found between US findings and other clinical parameters. US structural abnormalities may be a better differentiator of PsA and OA than PD signal. MRI validation of these results is pending.
Gisondi P, Idolazzi L, Girolomoni G. Ultrasonography reveals nail thickening in patients with chronic plaque psoriasis. Arch Dermatol Res 304:727–732,2012.
Acknowledgements This study was funded by a grant from UCB Australia Pty Ltd.
Disclosure of Interest None declared