Pain in right shoulder

Diagnosis: Rheumatoid arthritis

The patient’s history of morning stiffness and the joint erosion observed on x-ray were highly suggestive of rheumatoid arthritis (RA).

Joint stiffness due to osteoarthritis is worse with activity and generally lasts only a few minutes, while joint stiffness due to rheumatoid arthritis is worse at rest and lasts 30 minutes or more.

RA is a symmetric, inflammatory, peripheral polyarthritis of unknown etiology. It is the most common form of inflammatory arthritis, affecting 1% of the population worldwide.¹ It causes cartilage and bone to erode, leading to the deformation and destruction of joints. If RA is left untreated or is unresponsive to therapy, it can eventually lead to loss of physical function.

Making the diagnosis

The distinctive signs of RA are joint erosions and rheumatoid nodules, which are often absent on initial presentation.

Classification criteria. The 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria for RA² are based on the presence of synovitis in at least one joint, the absence of an alternative diagnosis that better explains the synovitis, and a cumulative score of at least 6/10 from the following 4 domains:

1. Number and site of involved joints
   • 2 to 10 large joints (shoulders, elbows, hips, knees, ankles)=1 point
   • 1 to 3 small joints (metacarpophalangeal [MCP] joints, proximal interphalangeal [PIP] joints, 2nd-5th metatarsophalangeal joints, thumb interphalangeal joints, wrists)=2 points
   • 4 to 10 small joints=3 points
   • More than 10 joints (including at least 1 small joint)=5 points
2. Serologic abnormality (rheumatoid factor [RF] and anti-cyclic citrullinated peptide)
   • Low positive=2 points
   • High positive=3 points
3. Elevated acute phase response (erythrocyte sedimentation rate [ESR] or C-reactive protein [CRP])=1 point
4. Symptom duration of at least 6 weeks=1 point.

These criteria are best suited for early disease. For patients with longstanding symptoms, diagnosis is based on an erosive disease with a history of criteria fulfillment, or a currently inactive longstanding disease, with or without treatment, that has previously fulfilled the criteria.³

Continue to: The differential Dx is extensive