Monarticular rheumatoid arthritis of the elbow

Background

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease manifested by polyarticular and symmetric joint inflammation.1 The worldwide prevalence of RA is about 0.5%–1% and occurs more frequently in middle-aged women.2 The exact aetiopathogenesis of RA is still unclear, but demographical, immunogenetic, epigenetic and environmental factors play important roles.3 The consequence of chronic joint inflammation in RA patients includes disability and poorer general health with increased morbidity and mortality.4

Classification for RA, as described by the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria, includes the presence of arthritis of multiple peripheral joints in association with elevated acute phase reactants (C reactive protein or erythrocyte sedimentation rate (ESR)), positive RA serological tests (rheumatoid factor (RF) and/or anti-cyclic citrullinated peptide (anti-CCP) antibody) and symptoms duration of 6 weeks or longer.5 The current classification system does not account for arthritis limited to a single large joint, nor does it include synovial tissue biopsy findings or imaging studies that may further assist in the diagnosis of RA. The elbow joint, considered a large joint by the ACR/EULAR criteria, is involved in up to 30% of cases of patients with RA.6 7 Furthermore, monarticular presentation of RA has been rarely reported.8 9 Here, we present a case of a middle-aged woman with monarticular RA of the elbow. To the best of our knowledge, only one case of RA limited the elbow has been previously reported.10

Case presentation

We present a middle-aged woman with arterial hypertension and a work-related trauma to the right arm and neck that occurred 5 years before our initial evaluation. Three years after the trauma, she began to experience neck pain and limited range of motion. An MRI of the cervical spine showed 25%–50% height loss of C4 vertebral body posteriorly and C5 central posterior compression deformity. One year later, she underwent posterior C4–C6 fusion, but the cervical wound did not heal well and was draining a serosanguineous fluid for which she was hospitalised for intravenous antibiotic therapy, and wound cleansing and debridement. She was discharged home to complete intravenous antibiotic therapy and receive hyperbaric oxygen therapy. She improved, but after 1 year she was hospitalised once again due to wound dehiscence and suppuration of the cervical wound requiring cervical spine cleansing and debridement surgery. Concurrently, she had a 1-year history of progressive right elbow pain, warmth, intermittent swelling and limited range of motion for which she was consulted to the rheumatology service. She had no history of arthralgias other than the right upper extremity and neck regions, and no tiredness, anorexia, weight loss, ocular symptoms, chest pain, cough, shortness of breath, abdominal pain, diarrhoea or skin rashes. Also, she had no family history of autoimmune rheumatic diseases such as RA, systemic lupus erythematosus, Sjogren’s syndrome, and psoriatic arthritis.

On initial physical examination, temperature was 36.4°C, heart rate was 80 beats per minute and blood pressure was 155/83 mm Hg. On musculoskeletal (MSK) examination, she had limited range of motion of the neck due to pain associated with recent surgical intervention and mild erythema. She had right elbow swelling, warmth, tenderness, crepitus and limited extension and flexion. In addition, she had right wrist limited range of motion due to a previous surgical fusion of the joint secondary to trauma. No other MSK abnormalities were found. She had no subcutaneous nodules. The rest of the physical examination was unremarkable.

Investigations

Laboratory tests revealed a white blood cell (WBC) count of 6.6 × 10⁹ /L, haemoglobin of 132 g/L and platelet count of 295 × 10⁹ /L. Blood urea nitrogen, serum creatinine levels and liver enzyme levels were normal. Urinalysis showed 0–3 red blood cells (RBC)/high-power field (hpf), 0–4 WBC/hpf and no proteinuria. Westergren ESR was 26 mm/hour. Anti-CCP antibodies were strongly positive at 217 units (normal range: <20 units), but RF was negative at 12.9 units/mL (normal range: 0–18 units/mL). Antinuclear antibodies were positive with a titre of 1:160 and a homogenous pattern. Anti-Smith, anti-ribonucleoprotein (RNP), anti-Ro and anti-La antibodies were negative. Complements C3 and C4 levels were normal.

Right elbow X-rays showed displacement of the anterior and posterior fat pad indicative of intra-articular joint effusion. No radiographical changes of degenerative joint disease were observed. Cervical spine MRI showed degenerative disease worse at C3–C4 level with posterior disc osteophytes and mild bilateral facet arthropathy causing moderate to severe spinal canal stenosis as well as mild right and moderate left neural foraminal stenosis. Right elbow MRI showed gross joint capsular distension with a heterogeneous intra-articular fluid component. In addition, fat saturation and short-tau inversion recovery sequences disclosed high-intensity signalling involving the bone marrow compartment of the proximal radius and ulna (figure 1). Synovial tissue biopsy revealed hyperplasia with an exuberant lymphoplasmacytic infiltrate with occasional multinucleated giant cells and focal acutely inflamed fibrinous deposits (figure 2). Synovial tissue and fluid cultures were negative. Examination of synovial fluid under polarised microscopy did not reveal crystals. Synovial fluid taken to determine cell count was clotted; therefore, the test could not be performed.

Differential diagnosis

In the setting of monarticular inflammation, the differential diagnosis includes seronegative inflammatory arthritis, trauma, crystal-induced arthropathy, septic arthritis and erosive/inflammatory osteoarthritis. However, these possibilities were excluded. She had no clinical or imaging findings consistent with psoriatic arthritis or reactive arthritis. Although she had a work-related trauma that involved her neck and right arm, she did not experience swelling or warmth of the right elbow until 3 years after the incident. In regards of a crystal-associated arthropathy, synovial fluid examination showed no evidence of crystals such as monosodium urate monohydrate, calcium pyrophosphate dehydrate or calcium oxalate crystals. Septic arthritis was excluded as synovial fluid and tissue cultures were negative. Finally, our patient had no radiographical evidence of osteoarthritis on plain X-ray of the right elbow. Although the synovial biopsy in patients with inflammatory osteoarthritis may present with non-specific synovitis, the presence of exuberant lymphoplasmacytic infiltrate and multinucleated giant cells, as in our case, is extremely unlikely.

Treatment

During the patient’s hospitalisation, she was not initially started on any disease-modifying antirheumatic drugs (DMARDs) due to concomitant infection with Staphylococcus epidermidis of the cervical wound. She was given intravenous antibiotic therapy for 10 days during hospitalisation and was discharged home to complete 14 days of oral antibiotics. Intra-articular corticosteroid injection of the elbow was recommended to reduce pain and inflammation, but the patient declined this option as she did not want the elbow to be manipulated any further.

Outcome and follow-up

Two months after discharge from the hospital, she had persistent pain and swelling of the right elbow. She was started on sulfasalazine 1 g orally two times per day. However, she did not tolerate sulfasalazine for which she was switched to methotrexate 7.5 mg orally weekly. She had a good response to this treatment. Seven months after discharge the patient has been doing well, with significant improvement of pain and swelling of the right elbow. During the follow-up period she did not develop any other peripheral joint involvement and no extra-articular manifestations.