What could be causing hand joint swelling and itching in an adult with possible autoimmune or injury history?

Hand Joint Swelling and Itching: Diagnostic Approach

The combination of hand joint swelling and itching most commonly suggests either inflammatory arthritis (particularly rheumatoid arthritis or psoriatic arthritis) with concurrent dermatologic involvement, or primary hand dermatitis complicated by secondary lymphedema, and requires urgent evaluation to distinguish between these entities. 1, 2, 3

Immediate Clinical Assessment

Key Historical Features to Elicit

• Morning stiffness duration >30 minutes strongly indicates inflammatory arthritis (rheumatoid arthritis or psoriatic arthritis), while stiffness <30 minutes suggests hand osteoarthritis with superimposed dermatitis 1, 2

• Itching characteristics matter: Primary eczematous conditions present with intense pruritus as the dominant symptom, whereas inflammatory arthritis presents with pain and swelling as primary complaints, with any itching being secondary 3

• Temporal relationship: Ask specifically whether joint swelling preceded itching or vice versa—this distinguishes primary arthritis with secondary skin changes from primary dermatitis with secondary joint involvement 3, 4

• Occupational exposures and hand hygiene practices are critical, as hand eczema (particularly pompholyx) is among the most frequent causes of itching hands and can lead to secondary lymphedema 3, 4

Physical Examination Priorities

Distinguish soft tissue swelling from bony enlargement: Inflammatory arthritis produces soft, boggy joint swelling from synovitis, while osteoarthritis causes hard, bony enlargement from osteophytes 1

Joint distribution pattern is diagnostic:

• Rheumatoid arthritis: Symmetric involvement of metacarpophalangeal (MCP) joints, proximal interphalangeal (PIP) joints, and wrists, typically sparing distal interphalangeal (DIP) joints 1, 2
• Psoriatic arthritis: May target DIP joints or affect entire digits (dactylitis/"sausage digits"), often asymmetric 2, 5
• Hand osteoarthritis: Primarily DIP joints (Heberden nodes) and PIP joints (Bouchard nodes) with bony enlargement 2

Perform the "squeeze test": Gentle compression across MCP joints or metatarsophalangeal joints elicits pain in inflammatory arthritis 1

Skin examination must assess for:

• Psoriatic plaques, nail pitting, or onycholysis (suggests psoriatic arthritis) 2
• Vesicular eruptions, scaling, or lichenification (suggests primary hand dermatitis) 3, 4
• Non-pitting edema of dorsal hands without tenderness (consider red puffy hand syndrome if history of IV drug use) 6

Essential Laboratory Workup

First-line serologic testing (order simultaneously):

• Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA/anti-CCP): ACPA has 90% specificity with 60% sensitivity for rheumatoid arthritis 1
• C-reactive protein (CRP) preferred over ESR—more reliable and not age-dependent 1
• Complete blood count with differential 1
• Comprehensive metabolic panel including liver and renal function 1

Critical interpretation: Normal CRP/ESR does not exclude inflammatory arthritis, as acute phase reactants can be normal even in active disease—prioritize clinical synovitis over laboratory values 1

If seronegative but clinical suspicion high: Seronegative rheumatoid arthritis accounts for 20-30% of cases and has similar prognosis to seropositive disease 1

Imaging Strategy

Baseline bilateral hand and wrist radiographs (posteroanterior view) are mandatory for all patients with joint swelling:

• Look for periarticular osteopenia, uniform joint space narrowing, and marginal erosions (inflammatory) versus asymmetric narrowing with osteophytes (osteoarthritis) 1, 2
• Presence of erosions on baseline films is highly predictive for rheumatoid arthritis diagnosis and disease persistence 1

Advanced imaging when diagnosis uncertain:

• Ultrasound with Power Doppler is 75% more accurate than physical examination alone for detecting subclinical synovitis and predicts disease progression 1
• MRI with IV contrast is more sensitive than ultrasound in early stages, detecting bone marrow edema (osteitis) which is the strongest predictor of future erosive progression 1

Algorithmic Diagnostic Approach

If Joint Swelling is Primary Complaint with Secondary Itching:

1. Inflammatory arthritis is most likely—refer to rheumatology within 6 weeks of symptom onset, as early treatment prevents irreversible joint damage 1, 2

2. Start methotrexate 15 mg weekly immediately as first-line DMARD without waiting for complete serologic workup, with plan to escalate to 20-25 mg weekly 1

3. Consider short-term low-dose prednisone (10-20 mg daily) as bridge therapy while awaiting DMARD effect 1

4. Screen for hepatitis B, hepatitis C, and tuberculosis before starting biologic agents if methotrexate proves inadequate 1

If Itching is Primary Complaint with Secondary Swelling:

1. Primary hand dermatitis with secondary lymphedema is most likely—particularly if bilateral pompholyx eczema with recurrent infections 4

2. Lymphoscintigraphy may reveal failure of small initial lymphatics to absorb and drain lymph, confirming lymphedema 4

3. Treatment requires: Prophylactic antibiotics for recurrent infections, aggressive management of dermatitis (often requiring systemic therapy), and lymphedema decongestion with occupational therapy 4

4. Do not mistake for inflammatory arthritis: Elevated rheumatoid factor may be present due to concurrent hepatitis C or other causes, leading to unnecessary immunosuppression 6

Critical Differential Diagnoses

Psoriatic arthritis: Look for psoriatic skin lesions or nail changes—psoriasis precedes arthritis in 72.7% of cases, RF typically negative, may have DIP involvement or dactylitis 2

Gout superimposed on hand osteoarthritis: MCPs (particularly index and middle fingers) and wrists most commonly affected, can complicate pre-existing osteoarthritis 5

Red puffy hand syndrome: Bilateral, painless, non-pitting erythema and edema of dorsal hands in patients with history of IV drug use—mistaken for rheumatoid arthritis leads to unnecessary immunosuppression 6

Ulcerative colitis-associated arthropathy: Type II peripheral arthropathy affects small joints of hands independently of bowel disease activity, seen in 2.5% of UC patients 7

Common Pitfalls to Avoid

• Do not delay treatment waiting for positive serology—seronegative rheumatoid arthritis is common (20-30% of cases) and has similar prognosis 1

• Do not dismiss inflammatory arthritis based on normal ESR/CRP—acute phase reactants are poor predictors and can be normal even in active disease 1

• Do not overlook primary dermatologic causes—hand eczema is one of the most frequent diagnoses in itching hands and can lead to secondary lymphedema mimicking arthritis 3, 4

• Do not assume elevated RF equals rheumatoid arthritis—RF can be elevated in hepatitis C, other autoimmune conditions, and even healthy individuals 6