Rheumatoid Arthritis (RA): articular manifestation
Introduction
- RA =
chronic, systemic, autoimmune inflammatory arthritis
- ลักษณะเด่น: symmetrical, peripheral joint inflammation
→ ถ้าไม่ได้ควบคุม
→ erosion, deformity, disability ภายใน 10–20
ปี
- มีผลต่อ กิจวัตรประจำวันและการทำงาน (เดิน,
ลุกนั่ง, เขียน, พิมพ์,
ใช้มือ)
- Extraarticular/systemic
features พบได้ใน ~40% ของผู้ป่วย (discussed
separately)
Initial Clinical Presentation
Patterns of Onset
- Classic
RA: gradual onset, polyarthritis, morning stiffness, hand/foot/wrist
involvement
- Palindromic
rheumatism (~episodic arthritis, hours–days, symptom-free intervals)
- 30–67%
progress to RA
- RF/ACPA
positivity ↑ risk
progression
- HCQ ลด risk of progression
- Monoarthritis:
large joint (wrist, knee, shoulder, hip, ankle) → อาจพัฒนาเป็น polyarthritis
- Proximal
arthritis: polymyalgia rheumatica (PMR)-like (proximal stiffness) → อาจเป็น early
RA
Key Symptom
- Morning
stiffness >1 hour →
hallmark of inflammatory arthritis (nonspecific, but strongly supportive)
Other systemic symptoms
- Aching,
stiffness, fatigue, depression, weight loss
- Carpal
tunnel syndrome อาจเป็นอาการนำ
- Elderly-onset
RA (> 60y): acute polyarthritis + myalgia, fatigue, fever,
weight loss
Specific Joint Involvement
Hands
- Early:
pain, swelling, ↓ grip
strength, squeeze tenderness
- Signs:
dorsal hand swelling (“boxing glove”), palmar tendon
thickening/tenosynovitis, nodules →
tendon rupture
- Carpal
tunnel (1–5% as initial presentation)
- Deformities
(late): MCP subluxation, ulnar drift, swan neck, boutonnière, “bow string
sign”
Wrists, Elbows, Shoulders
- Wrists:
early involvement, loss of extension, late = volar subluxation, radial
drift, tendon rupture
- Elbows:
effusion, flexion deformity, olecranon bursitis, ulnar neuropathy,
subcutaneous nodules
- Shoulders:
late disease → painful
restriction, frozen shoulder, rotator cuff tear
Feet/Ankles
- Early:
MTP involvement (esp. 5th MTP) →
tenderness, squeeze test
- Deformities:
lateral drift of toes, cock-up deformities, plantar subluxation → callosities
- Ankle:
diffuse swelling (may mimic cellulitis), pain on inversion/eversion
- Heel
pain: retrocalcaneal bursitis, tarsal tunnel syndrome
Knees/Hips
- Knees:
synovial thickening, effusion (patellar tap), restricted ROM, valgus/varus
deformity, Baker’s cyst (rupture →
mimic DVT)
- Hips:
longstanding RA, groin/thigh/back pain, restricted rotation, sometimes
trochanteric bursitis
Axial Skeleton
- Cervical
spine (C1–C2 subluxation) →
risk cord compression, myelopathy, hyperreflexia, Babinski sign
- Other
axial joints: TMJ, SCJ, ACJ, cricoarytenoid (hoarseness/stridor, rare in
biologic era)
Laboratory Findings
- Synovial
fluid: inflammatory (WBC 1500–25,000, PMN predominant), low
complement, occasionally low glucose
- Hematology:
anemia of chronic disease, thrombocytosis, mild leukocytosis, ↑ lymphoma risk, rarely
Felty’s syndrome or LGL leukemia
- Autoantibodies:
RF and/or ACPA (+) ใน 75–80%
- RF:
sensitive but less specific
- ACPA:
similar sensitivity, much more specific
- ANA:
25–30% (clinical significance limited, but SSA+ = risk neonatal
lupus/heart block)
- Acute
phase reactants: ESR, CRP usually ↑
and correlate with activity
Imaging
- Plain
radiographs (hands/feet):
- Early:
soft tissue swelling, periarticular osteopenia
- Later:
erosions, joint space narrowing, subluxations, deformity
- By
2 years untreated →
erosions in ~90%
- MRI:
- Detects
erosions earlier (7x more than X-ray)
- Bone
marrow edema = predictor of future erosions
- Detects
synovial hypertrophy/proliferation
- Ultrasound:
- Sensitive
for synovitis, effusion, erosions (esp. MTP)
- Doppler
activity correlates with inflammation
Clinical Course
- Variable:
small vs large joints, number of joints, disease activity fluctuations,
remission vs progression
- Disease
activity: fluctuates (weeks–months), DMARDs ↑ chance of remission
- Damage:
cumulative, irreversible, linked to inflammation + mechanical stress
- Remission:
- Rare
without DMARDs
- Defined
by ACR/EULAR criteria (CDAI, SDAI, Boolean 2.0)
- Radiographic
progression can still occur in remission
Key Pearls
- Classic
triad: symmetric polyarthritis + morning stiffness >1 hr + small
joint involvement (MCP, PIP, MTP, wrists)
- Red
flags: cervical spine pain, acute neurologic signs → suspect subluxation
- Prognosis:
worse with high RF/ACPA titers, early erosions, high inflammatory markers,
extraarticular disease
- Goal:
early aggressive DMARDs to induce remission, prevent erosions, preserve
function
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