Rheumatoide Arthritis (RA)
RA is a chronic, systemic, inflammatory disorder of unknown etiology that is characterized by its pattern of diarthrodial joint involvement. Its primary site of pathology is the synovium of the joints. The synovial tissues become inflamed and proliferate, forming pannus that invades bone, cartilage, and ligaments and leads to damage and deformities. Rheumatoid factor (RF), anticitrullinated protein antibodies (ACPAs), and extraarticular manifestations commonly accompany the joint disease, but arthritis represents the major manifestation.
- Rheumatoid arthritis (RA) is the most common chronic inflammatory arthritis.
- Symmetric synovitis of the small joints of the hands (metacarpophalangeal joints [MCPs], proximal interphalangeal joints [PIPs]) and wrists is the classic initial pattern.
- RA patients with extraarticular manifestations should be seropositive.
- Early and aggressive therapy should target low disease activity for optimal outcomes.
- RA patients have accelerated atherosclerosis warranting aggressive risk factor modification.
According to the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) criteria, to be classified as having RA, a patient must satisfy ≥6 out of 10 points. The criteria demonstrate 82% sensitivity and 61% specificity for RA when compared with control subjects with non-RA rheumatic disease.
Most Common Joints Involved During the Course of RA:
90% to 95%
50% to 60%
75% to 90%
Cervical spine (esp. C1–C2)
40% to 50%
75% to 80%
40% to 50%
60% to 80%
20% to 40%
50% to 70%
10% to 30%
50% to 60%
MCP, Metacarpophalangeal joint; MTP, metatarsophalangeal joint; PIP, proximal interphalangeal joint; RA, of rheumatoid arthritis.
Typical laboratory findings in RA patients:
CBC: anemia of chronic disease and thrombocytosis correlate with active disease. The WBC count and the differential should be normal unless the patient has Felty’s syndrome or another disease.
Chemistries: normal renal, hepatic, and uric acid tests. Albumin may be low in active disease because it is a negative acute phase reactant.
Erythrocyte sedimentation rate (ESR): usually elevated. Can be normal in patients with early limited disease. ESR can be elevated as a result of inflammation and hypergammaglobulinemia.
CRP: usually elevated. Better to follow disease activity than ESR because it is not influenced by hypergammaglobulinemia.
Rheumatoid factor (RF): positive in 70% to 80% with a specificity of 86% for RA. RF positivity is associated with more severe disease, with extraarticular manifestations including subcutaneous nodules, and with increased mortality.
Anti-CCP: positive in 57% to 66%. It has a high specificity for RA (93% to 97%) although it has been reported in patients with psoriatic arthritis with symmetric arthritis (10%) and in patients with tuberculosis (TB).
Antinuclear antibodies (ANA): positive in 30%. However, they are not directed against any specific antigens (e.g., SS-A, SS-B, RNP, Sm, dsDNA). ANA-positive patients tend to have more severe disease and a poorer prognosis than RA patients who are ANA-negative.
ANCA: usually negative. If it is positive, it should not have specificity against PR3 or myeloperoxidase.
Complement (C3, C4, CH50): normal or elevated. If it is low, consider a disease other than RA.
Radiographic features of RA:
The mnemonic ABCDE’S is a convenient way to remember these:
A—Alignment, abnormal; no ankylosis
B—Bones—periarticular (juxta-articular) osteoporosis; no periostitis or osteophytes
C—Cartilage—uniform (symmetric) joint-space loss in weight-bearing joints; no cartilage or soft tissue calcification
D—Deformities (swan neck, ulnar deviation, boutonnière) with symmetrical distribution
S—Soft-tissue swelling; nodules without calcification