What is the diagnosis and treatment for swollen painless knuckles and rough skin on the fingers?

Diagnosis: Psoriatic Arthritis with Skin Manifestations

The combination of swollen painless knuckles and rough skin on the fingers strongly suggests psoriatic arthritis (PsA), particularly when presenting with nail changes and skin involvement over the finger joints. 1

Key Diagnostic Features

The clinical presentation described is characteristic of PsA affecting the hands:

• Swollen painless knuckles likely represent dactylitis ("sausage digit"), which is a hallmark of PsA occurring in 16-48% of cases, resulting from a combination of enthesitis of tendons and ligaments along with synovitis involving the whole digit 1
• Rough skin on the fingers may indicate psoriatic plaques or nail dystrophy, which is commonly found in patients with PsA, especially those with distal interphalangeal joint involvement 1
• The painless nature is notable, as acute dactylitis can present without significant tenderness in some cases, though chronic non-tender diffuse dactylitic swelling may be less clinically significant 1

Critical Assessment Points

When evaluating this presentation, examine for:

• Nail changes: pitting, onycholysis, or severe nail dystrophy, which strongly correlate with PsA 1
• Psoriatic skin lesions: check scalp, elbows, knees, genitals, and other areas for characteristic plaques 1
• Morning stiffness: ask specifically about early morning stiffness lasting longer than 30 minutes, which is valuable for diagnosing PsA 1
• Pattern of joint involvement: PsA commonly affects distal interphalangeal joints and metacarpal-phalangeal joints 1

Differential Diagnosis Considerations

While PsA is most likely, consider:

• Knuckle pads: benign fibrotic thickening over knuckles, but these would not explain joint swelling 2
• Hand eczema: can cause rough skin but typically doesn't cause joint swelling 2
• Other inflammatory arthropathies: however, the combination with rough skin on fingers makes PsA most probable 1

Recommended Diagnostic Workup

• Rheumatology referral is warranted for definitive diagnosis, particularly if you are unsure, as rheumatologists will perform comprehensive joint assessment including tender and swollen joint counts 1
• Laboratory testing: check rheumatoid factor (typically negative in PsA), C-reactive protein, and erythrocyte sedimentation rate to measure systemic inflammation 1
• Imaging: X-rays may show characteristic findings, though no specific serologic or genetic test is available in the United States to definitively diagnose PsA 1

Treatment Algorithm

For Mild PsA:

• NSAIDs alone as first-line therapy 1
• If unresponsive after 2-3 months, escalate to methotrexate 1

For Moderate to Severe PsA:

• Methotrexate, TNF-alpha blockade, or combination therapy is considered first-line treatment 1
• Methotrexate is often used first before TNF-alpha blockade primarily due to significantly lower cost, despite limited evidence from only two small randomized placebo-controlled studies 1
• For patients with inadequate response to methotrexate monotherapy, combination of oral cyclosporine with oral methotrexate can be effective 1

For Dactylitis Specifically:

• Treatment is largely empirical and follows the general PsA treatment algorithm 1
• Recurrent isolated dactylitis may be the only clinical manifestation of PsA and requires systemic therapy 1

Critical Pitfalls to Avoid

• Do not delay treatment: Left untreated, patients with PsA can have persistent inflammation, progressive joint damage, severe physical limitations, and disability 1
• Severity of skin and joint disease do not correlate: patients may have severe PsA with minimal skin disease 1
• Early detection is crucial: radiographic damage can occur in 7-47% of patients at a median interval of 2 years despite clinical improvement with standard therapy 1
• Dermatologists are uniquely positioned to detect early PsA since the vast majority of patients have cutaneous manifestations for up to 12 years before onset of joint disease 1