OR5.1 | Inflammatory Arthritis — Glossary

Inflammation of the anterior uvea (iris and ciliary body), presenting as acute unilateral painful red eye with photophobia and reduced vision; occurs in 25–40% of AS patients and is the most common extra-articular manifestation of spondyloarthropathies.

Autoantibody directed against cyclic citrullinated peptides; sensitivity ~70% for RA with specificity ~95% — the most specific serological marker for RA and a predictor of more erosive disease course.

The classic radiological appearance of advanced ankylosing spondylitis: the entire spinal column bridged by contiguous syndesmophytes and fused facet joints, resembling a length of bamboo on plain X-ray.

An RA finger deformity caused by central slip rupture: the PIP joint falls into flexion while the DIP joint hyperextends, creating a 'buttonhole' appearance through the lateral bands of the extensor apparatus.

Post-translational modification of arginine residues to citrulline in proteins, promoted by cigarette smoking and inflammation; citrullinated peptides are the primary antigenic targets of anti-CCP antibodies in the autoimmune pathogenesis of RA.

Diffuse inflammatory swelling of an entire finger or toe ('sausage digit') from simultaneous flexor tendon sheath inflammation and small joint synovitis; a pathognomonic feature of psoriatic arthritis (and reactive arthritis) that is essentially absent in RA.

A drug class that alters the underlying immunopathological process in inflammatory arthritis, preventing joint erosion and disability — in contrast to NSAIDs and analgesics, which provide only symptomatic relief without modifying the disease course.

Inflammation at the point where a tendon, ligament, or joint capsule inserts into bone (the enthesis); the pathological hallmark of spondyloarthropathies, distinguishing them from the synovitis-predominant pathology of RA.

A human leukocyte antigen class I allele present in >90% of ankylosing spondylitis patients versus 8–10% of the Indian general population; central to the immunopathogenesis of seronegative spondyloarthropathies through the arthritogenic peptide hypothesis.

A folate antagonist DMARD administered weekly (7.5–25 mg/week) as the anchor first-line therapy for RA; prevents erosions and disability; absolutely contraindicated in pregnancy due to teratogenicity and risk of fetal death.

Separation of the nail plate from the nail bed, appearing as yellowish-white discolouration from the free edge; a nail change strongly associated with psoriasis and psoriatic arthritis, particularly when DIP joints are involved.

A proliferative sheet of activated synovial fibroblasts and macrophages that overhangs and erodes articular cartilage and subchondral bone at the 'bare area' (cartilage-synovium junction); the destructive lesion responsible for irreversible joint damage in RA.

A radiological hallmark of psoriatic arthritis in its mutilans form: resorption of the distal phalanx creates a sharpened 'pencil point' that articulates with a cup-shaped erosion on the proximal phalanx base; unique to PsA.

Simultaneous inflammation of five or more joints; classifying the pattern (symmetric vs asymmetric, large vs small, axial vs peripheral, seropositive vs seronegative) is the cornerstone of the diagnostic approach to inflammatory joint disease.

An IgM autoantibody directed against the Fc portion of IgG; positive in approximately 70% of RA patients but also elevated in chronic infections and other autoimmune diseases — sensitivity ~70%, specificity ~80% for RA.

Inflammation of the sacroiliac joints; the earliest and most consistent radiological finding in ankylosing spondylitis, presenting as bilateral symmetrical joint space changes, sclerosis, and eventual fusion on plain X-ray.

A clinical test of lumbar spinal mobility: marks placed 5 cm below and 10 cm above the lumbosacral junction with the patient standing; after maximal forward flexion the inter-mark distance should increase by ≥5 cm — a smaller increment indicates reduced lumbar mobility as seen in ankylosing spondylitis.

Inflammatory arthritis in which rheumatoid factor and anti-CCP antibodies are absent; the seronegative spondyloarthropathies (AS, PsA, reactive arthritis, enteropathic arthritis) form the main group, though a minority of RA patients are also seronegative.

A group of seronegative (RF-negative) inflammatory arthritides sharing axial skeleton and enthesis involvement, HLA-B27 association, and familial clustering; includes ankylosing spondylitis, psoriatic arthritis (axial type), reactive arthritis, and enteropathic arthritis.

An RA finger deformity: PIP joint hyperextension combined with DIP flexion, caused by volar plate laxity and intrinsic muscle tightening; functionally impairs fine grip and pinch.

A bony bridge formed by ossification of the outer annulus fibrosus between adjacent vertebral bodies; contiguous and marginal in AS (ascending sequentially from sacrum to cervical spine), producing the bamboo spine; non-marginal and non-contiguous ('skip lesions') in psoriatic arthritis.

Inflammation of the synovial membrane lining a joint, producing warmth, swelling, and a boggy non-bony effusion; the primary pathological lesion in rheumatoid arthritis.

A characteristic RA deformity of the fingers at the MCP joints: volar subluxation and ulnar drift caused by capsular and ligamentous damage combined with extensor tendon displacement toward the ulnar side.