Arthralgia and joint deformity, rheumatoid arthritis? or nail-patella syndrome?

Abstract

Background: Nail-patella syndrome (NPS) is a rare autosomal dominant systemic disorder that is characterized by dysplasia of the nails, hypoplasia or aplasia of the patella, dislocation of the elbow and the presence of iliac horns. Rheumatoid arthritis (RA) is an autoimmune disorder of the joints characterized by inflammatory arthritis and subsequent joint destruction. Of note, NPS and RA share some musculoskeletal symptoms such as swan-neck deformities of the fingers and joint dislocation, and renal and neural involvement is also observed in these diseases. The prevalences of NPS and RA are 1/50000 and 1/100-1/200, respectively, while no case of NPS co-existing with RA has been reported. Case presentation: Here, we present the first reported case of nail-patella syndrome co-existing with rheumatoid arthritis. A 74-year-old man who had a past history of glaucoma and elbow dislocation was admitted to our hospital due to an 8-month history of arthralgia in bilateral wrists, elbows and fingers. An X-ray showed deformity of bilateral radial heads and joint space narrowing in the right elbow, and magnetic resonance imaging of his hands showed synovitis and erosion in the multiple swollen joints of the wrists and fingers. In addition to these typical features of rheumatoid arthritis, he had bilateral thumb nail dysplasia with mild hypoplasia of bilateral patella and iliac horns as shown by the X-ray. He was diagnosed as having autosomal dominant disorder nail-patella syndrome co-existing with rheumatoid arthritis and he was treated with methotrexate in combination with an oral Janus kinase (JAK) inhibitor, leading to induction of remission. Conclusions: On the basis of their prevalences, the coexistence of nail-patella syndrome and rheumatoid arthritis with overlapped features, including arthralgia, joint deformity and dislocation, glomerulonephritis and neurological abnormality, could be observed in real-world clinical practice. Since the therapeutic strategy for and the prognosis of these diseases are different, appropriate diagnosis based on clinical and radiographic findings is required to improve future prognosis. (314 words)