Background/Purpose: Cystic fibrosis (CF) is the most common lethal autosomal recessive genetic disorder. The improvement in life expectancy due to the advent of new treatments has led to an increase in extrapulmonary manifestations, such as joint involvement. Few studies have focused on joint manifestations in CF patients. This study aims to describe the joint phenotypes observed in CF patients and to investigate factors that may influence joint flares, such as bronchial infections, antibiotic therapy, or the introduction of long-term treatments.

Methods: This is a monocentric, descriptive, retrospective study conducted in adult CF patients followed between 2008 and 2022. Using data from the Department of Medical Information and from the pulmonology department of our Hospital, we identified CF patients who presented with arthritis and/or joint pain and consulted in rheumatology.

Results: Fifteen patients (60% women) followed for CF in the pulmonology department of our Hospital reported rheumatic symptoms (arthritis and/or arthralgia) that warranted consultation or follow-up in rheumatology. The average age was 39 years, 20% of the patients had undergone lung transplantation, and 10 patients were on Ivacaftor. Three clinical joint phenotypes were observed:

• Rheumatoid Arthritis (RA): 5 patients had RA with positive anti-CCP antibodies and structural damage in 4 cases.
• Chronic Non-Destructive Inflammatory Rheumatism (CNDIR): 5 patients exhibited CNDIR. This included 1 patient with psoriatic arthritis (oligoarticular involvement of small joints with associated osteitis), 3 patients with unclassified CNDIR (2 with polyarticular involvement, 1 with oligoarticular involvement affecting large joints), and 1 patient with an autoinflammatory syndrome.
• Non-Specific Polyarthralgia: 5 patients displayed non-specific polyarthralgia.

Among the 10 patients with RA or CNDIR, 6 were on Methotrexate, 3 on biologics (Rituximab, Anti-TNF, Anti-IL12/23), and 5 on corticosteroids (5 to 10 mg/day), all with good tolerance, notably no severe infection.

For these three phenotypes, it was challenging to retrospectively assess the effect of bronchial infections, antibiotic therapy, and/or Ivacaftor treatment on the occurrence of joint flares.

Conclusion: We identified three distinct clinical phenotypes: patients with genuine RA, patients with non-destructive CNDIR, and patients with non-specific polyarthralgia. The incidence of RA in our CF population was high (1/3 of patients), indicating a close lung-joint connection in this rheumatism. Treatment with corticosteroids, Methotrexate, and/or biologics did not appear to increase infectious risk. The impact of bronchial infections, their antibiotic treatment, and long-term Ivacaftor therapy (which reduces bronchial inflammation) will be studied prospectively through systematic rheumatological evaluation of CF patients presenting with arthritis or inflammatory arthralgia.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/joint-involvement-in-cystic-fibrosis-description-of-clinical-phenotypes/