Chronic Plaque Psoriasis with New-Onset Joint Pain and Fatigue
A 44-year-old man with a 12-year history of chronic plaque psoriasis, previously managed with topical corticosteroids and narrowband UVB, presents with a 3-month history of pain and swelling in the right knee, left ankle, and both wrists. He also reports morning stiffness lasting 90 minutes and fatigue. Examination shows erythematous scaly plaques over the elbows, knees, and scalp (PASI 12), and swelling of the right knee and left ankle with tenderness. Nails show pitting and onycholysis. He has no history of gout, and rheumatoid factor and anti-CCP are negative. He is HLA-B27 positive. Recent labs: CRP 18 mg/L, ESR 42 mm/h. He is currently applying clobetasol propionate 0.05% cream twice daily to all plaques.
1. What is the most likely diagnosis, and how would you confirm it?
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The most likely diagnosis is psoriatic arthritis (PsA), specifically the oligoarticular subtype with involvement of the knee, ankle, and wrists, given the long-standing psoriasis, nail changes (pitting and onycholysis are strong predictors of PsA), negative RF/anti-CCP, and elevated inflammatory markers. Confirmation is clinical, based on CASPAR criteria (psoriasis, nail dystrophy, negative RF, dactylitis, juxta-articular new bone formation). Imaging with plain radiographs of the affected joints may show erosions, periostitis, or 'pencil-in-cup' changes, but early disease may be normal. Ultrasound or MRI can detect synovitis and enthesitis. Referral to rheumatology is warranted for formal assessment and treatment.
2. How would you adjust his current topical therapy, and what systemic options would you consider?
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His current use of clobetasol 0.05% twice daily to all plaques is excessive and risks adrenal suppression and skin atrophy, especially over large areas. I would reduce to once daily for 2–4 weeks, then taper to intermittent use (e.g., weekends) and switch to a less potent agent for maintenance. For PsA, systemic therapy is indicated. Methotrexate (15–20 mg weekly with folic acid) is a reasonable first-line DMARD that treats both skin and joints. If inadequate response or contraindicated, consider biologics such as TNF inhibitors (adalimumab, etanercept) or IL-17 inhibitors (secukinumab, ixekizumab), which are effective for both psoriasis and PsA. IL-23 inhibitors (guselkumab, risankizumab) are also options. NSAIDs can be used for symptom relief but may worsen psoriasis. Regular monitoring of liver function, blood counts, and lipids is needed with methotrexate.
3. What factors would influence your choice between methotrexate and a biologic?
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Factors favoring methotrexate: mild-to-moderate joint involvement, absence of significant comorbidities (e.g., liver disease, renal impairment, excessive alcohol use), patient preference for a pill, cost and access, and need for concomitant treatment of skin. Factors favoring a biologic: severe or erosive joint disease, inadequate response or intolerance to methotrexate, significant psoriasis (PASI >10) with high impact on quality of life, presence of comorbidities such as metabolic syndrome or fatty liver disease (where methotrexate is relatively contraindicated), and patient preference for injectable therapy. Also consider tuberculosis screening before biologics, and hepatitis B/C status. Shared decision-making with the patient and rheumatologist is essential.