In the first descriptions of psoriatic arthritis (PsA),1,2 Wright described a subtype of patients who had involvement of the distal interphalangeal joints with erosion and resorption of the joint ends and a characteristic shortening of the fingers that he called mutilating arthritis (MA). Apart from the first PsA series published by Wright,1,2 few studies3–6 have mentioned these mutilating forms. In the largest series PsA published to date,4,7–11 the prevalence varies enormously, ranging between 2% and 23%.

There is some confusion in the terminology used (“opera-glass hand syndrome,”12, “main in lorgnette,”13 “arthritis mutilans” or “resorptive arthropathy”5).

The objective of this study was to describe the frequency of MA and study its relationship with other variants of PsA.

This was an observational, cross-sectional multicenter PsA study performed in 8 rheumatology centers. All patients met CASPAR14 criteria. The recorded variables are shown in Table 1. We performed an anteroposterior X-ray of the hands and feet in those patients with clinical deformity indicative of MA (shortened fingers) or clinical signs of inflammatory activity in these locations. The patient was considered as having resorptive arthropathy if hands and feet radiographs showed at least one joint with both bone ends shortened without osteophytes.

Twenty-four patients (6.7%) were diagnosed with MA. The description of the patients is shown in Table 2. The analysis of the different variables in the subgroup of patients with bone resorption and the rest of the patients in the PsA series are shown in Table 1. The duration of arthritis was significantly greater (p<.05) in patients with bone resorption. The distal interphalangeal involvement was significantly more common in patients with resorptive changes (p=.00).

Functional capacity was worse in this subset of patients, both in the case of that perceived by the physician as well as that according to the ACR scale (p=.05) and self-perceived by the patient in the self-administered mHAQ questionnaire (p=.001). We observed a higher concentration of MA in tertiary health centers (p=.015).

Multivariate analysis showed an association between independent variables of duration of arthritis, distal interphalangeal condition and mHAQ with regard to the dependent variable (presence or absence of MA).

The term “arthritis mutilans” generally refers to severe deformities and recalls the “opera glass syndrome” appearance of multiple shortened fingers. But sometimes the resorptive process is not as marked as we have shown in this study, because one third of our patients had less than 3 affected fingers. When the process is limited to the feet it may go unnoticed and 20% in our series had a resorption process limited to the feet. For this reason, we believe that the term “resorptive arthropathy”, based on the X-ray image and coined by Swezey et al.5 better reflects the nature of the process. The “opera glass hand” deformity would be the final stage for some patients where juxtaarticular bone resorption is more severe.

The exact prevalence of MA/resorptive arthropathy in PsA shows very different results that we believe are due to the very heterogeneous definitions used in published series. Our prevalence is slightly higher than other series (6.7%) because we believe that we have included milder forms manifested only in X-rays. When only considering the “opera glass syndrome”, the prevalence in our series is 1.94% and if we take into consideration only those patients who are clinically shown to have shortening of any finger, the frequency of hand or foot affection is 4.4%. When compared with larger and recent ones,4 which use expert opinion consensus or the CASPAR definition of ‘arthritis mutilans’, prevalence is 3.7%.

Most of the joint pattern involved is polyarticular and symmetrical, as we and other authors4 have shown. We have to note that 12.5% of our patients with MA/resorptive arthropathy have an oligoarticular form.

We also observed an association with a longer duration of arthritis, distal interphalangeal involvement and a worse functional capacity measured by the HAQ score and ACR functional scale. CASPAR4 study data also show an association with increased duration of arthritis, but instead do not show a worse functional capacity according to the HAQ score. The fact that it is associated with a longer duration of arthritis can lead one to believe that MA/resorptive arthropathy is a consequence of the inflammatory process in time longer.

One of the incidental findings that was striking in our study is the high frequency (30%) of the association findings of MA and nodular osteoarthritis. The prevalence of nodular osteoarthritis in normal population over 40 years is less than 8.5%.15 We have not found any publication describing this association.

The authors have no conflict of interest to make.