Radiographic development during three decades in a patient with psoriatic arthritis mutilans

Rare coding variants in NOX4 link high ROS levels to psoriatic arthritis mutilans

Psoriatic arthritis mutilans (PAM) is the rarest and most severe form of psoriatic arthritis, characterized by erosions of the small joints and osteolysis leading to joint disruption. Despite its severity, the underlying mechanisms are unknown, and no susceptibility genes have hitherto been identified. We aimed to investigate the genetic basis of PAM by performing massive parallel sequencing in sixty-one patients from the PAM Nordic cohort. We found rare variants in the NADPH oxidase 4 (NOX4) in four patients. In silico predictions show that the identified variants are potentially damaging. NOXs are the only enzymes producing reactive oxygen species (ROS). NOX4 is specifically involved in the differentiation of osteoclasts, the cells implicated in bone resorption. Functional follow-up studies using cell culture, zebrafish models, and measurement of ROS in patients uncovered that these NOX4 variants increase ROS levels both in vitro and in vivo. We propose NOX4 as the first candidate susceptibility gene for PAM. Our study links high levels of ROS caused by NOX4 variants to the development of PAM, offering a potential therapeutic target.

Comorbidities in a Cohort of 66 Patients With Psoriatic Arthritis Mutilans-Results From the Nordic PAM Study

Objective: Psoriatic arthritis mutilans (PAM) is the most severe phenotype of psoriatic arthritis due to excessive bone erosion causing joint destruction and decreased functional capacity. The aim of this study was to investigate the prevalence of comorbidities among patients with PAM and the association between comorbidities and joint involvement. Methods: A total of 66 patients aged ≥18 years from the Nordic countries with past or present psoriasis along with at least one mutilated joint were included in the present study. Results: The median number of comorbid conditions per patient was 1 [interquartile range (IQR) 0-2] and 16.7% reported three or more comorbidities. The most frequent comorbidity was hypertension (36.4%). The median number of mutilated joints per patient was 3 (IQR 1-8.3; range 1-38). Conclusion: Two thirds of the patients with PAM reported comorbid conditions and the most frequent was hypertension which affected more than a third of the patients. However, this study was unable to detect any association between comorbidities and the severity of PAM.

Radiographic scoring systems for psoriatic arthritis are insufficient for psoriatic arthritis mutilans: results from the Nordic PAM Study

Background

Psoriatic arthritis mutilans (PAM) is the most severe phenotype of psoriatic arthritis (PsA).

Purpose

To describe the radiological features in PAM and explore whether existing scoring systems for radiological damage in psoriatic arthritis are applicable for PAM.

Material and Methods

Radiographs were scored according to the modified Sharp-van der Heijde (mSvdH) and the Psoriatic Arthritis Ratingen Score (PARS) systems for PsA.

Results

At inclusion, 55 PAM patients (49% women, mean age 58 ± 12 years) had conventional radiographs of both hands and feet. A total of 869 PAM joints were detected and 193 joints with ankylosis. The mean total mSvdH score was 213.7 ± 137.8 (41% of maximum) with a higher score for hands than for feet: 136.6 ± 90.1 vs. 79.1 ± 60.9. However, the total score was relatively higher in the feet than in the hands when compared to the highest possible scoring (47% vs. 38% of max). The mean total PARS score was 126.3 ± 79.6 (35% of max). Scoring for joint destruction was higher than for proliferation (22% vs. 11% of max). Strong correlation was found between mSvdH and PARS (r² = 0.913). A significant correlation was found between scoring and duration of arthritis and the Health Assessment Questionnaire. History of smoking, BMI, and gender did not influence the scoring values.

Conclusions

The two scoring systems studied may not be ideal to indicate progression of PAM in advanced disease since they reach ceiling effects rather early. Therefore, reporting early signs suggestive of PAM, e.g. signs of pencil-in-cup deformities or osteolysis, is crucial. This would reveal the presence of PAM and might lead to improved treatment in order to minimize joint damage.