Psoriasis is a systemic immune-mediated disease driven by T-cell dysregulation. The skin is the visible manifestation — but the joints, cardiovascular system, and metabolic health are all affected. Treating psoriasis means treating the whole patient, not just the plaques.
CLINICAL PRINTABLE
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A one-page Psoriasis clinical reference is on the way.
1 · Recognition
- Classic plaque psoriasis: well-demarcated, erythematous plaques with silvery-white scale. Predilection for extensor surfaces (elbows, knees), scalp, and lumbosacral area. Auspitz sign: pinpoint bleeding when scale is removed.
- Psoriasis variants: guttate (small teardrop-shaped lesions, often post-streptococcal), inverse (smooth erythema in skin folds without scale), pustular (sterile pustules, can be generalized and life-threatening), erythrodermic (widespread erythema, medical emergency).
- Nail psoriasis: pitting, onycholysis (nail plate separation), oil-drop sign (salmon-colored subungual discoloration), subungual hyperkeratosis. Nail involvement is associated with higher risk of psoriatic arthritis.
- Psoriatic arthritis: asymmetric oligoarthritis, DIP joint involvement, dactylitis (sausage digit), enthesitis (tendon/ligament insertion inflammation), axial disease. Screen all psoriasis patients at every visit.
- Comorbidities: metabolic syndrome, cardiovascular disease, depression, inflammatory bowel disease, uveitis. Psoriasis is an independent cardiovascular risk factor — address modifiable CV risk factors.
2 · Differential / Mimics
Seborrheic dermatitis
Greasy yellow scale on scalp, face, and chest. Lacks the thick silvery scale and extensor distribution of psoriasis. Responds to antifungals.
Eczema / atopic dermatitis
Flexural distribution (antecubital, popliteal fossae), intense pruritus, personal/family atopy history. Lacks the well-demarcated silvery plaques of psoriasis.
Tinea corporis
Annular scaly plaques with central clearing. KOH prep positive. Topical antifungal is curative — do not treat with steroids alone.
Pityriasis rosea
Herald patch followed by Christmas tree distribution on trunk. Self-limited over 6–8 weeks. Associated with HHV-6/7 reactivation.
3 · Treatment Pathway
Mild psoriasis (< 3% BSA, limited impact)
Topical corticosteroids as first-line — potency matched to body site (low-potency for face/folds, mid-high potency for body/scalp). Topical vitamin D analogs (calcipotriene) as steroid-sparing alternative or combination. Coal tar for scalp.
Moderate psoriasis (3–10% BSA or significant impact)
Topical therapy plus phototherapy (narrowband UVB preferred). Phototherapy is highly effective and safe for long-term use. Consider systemic therapy if phototherapy is impractical.
Severe psoriasis (> 10% BSA, disabling, or joint involvement)
Systemic therapy: methotrexate, cyclosporine (short-term), acitretin (for pustular/erythrodermic). Biologics (TNF inhibitors, IL-17 inhibitors, IL-23 inhibitors) for moderate-severe or biologic-appropriate disease.
Biologic selection
IL-17 inhibitors (secukinumab, ixekizumab) and IL-23 inhibitors (guselkumab, risankizumab) have highest skin clearance rates. TNF inhibitors (adalimumab, etanercept) also treat psoriatic arthritis. Screen for TB and hepatitis B before initiating biologics.
Psoriatic arthritis
NSAIDs for mild joint disease. DMARDs (methotrexate, sulfasalazine) for peripheral arthritis. TNF inhibitors or IL-17 inhibitors for moderate-severe PsA — these treat both skin and joints. Rheumatology co-management.
4 · Expected Response
- Topical corticosteroids: improvement within 2–4 weeks. Avoid continuous use on the same area — rotate with steroid-sparing agents to prevent atrophy, striae, and tachyphylaxis.
- Narrowband UVB: 3 sessions per week, typically 20–30 sessions for initial clearance. Maintenance therapy reduces relapse frequency.
- Biologics: significant improvement at 12–16 weeks. PASI 75 (75% reduction in Psoriasis Area and Severity Index) is the standard efficacy benchmark. Many patients achieve PASI 90 or 100 with IL-17/IL-23 inhibitors.
- Methotrexate: onset 4–8 weeks. Monitor CBC and LFTs at baseline and periodically. Folic acid 1 mg daily reduces side effects. Cumulative dose monitoring for hepatotoxicity.
5 · Escalation
- Erythrodermic psoriasis: >90% BSA erythema with systemic instability (fever, hypothermia, electrolyte disturbances, high-output cardiac failure) — hospitalization, dermatology, and internal medicine co-management.
- Generalized pustular psoriasis: widespread sterile pustules with fever and systemic toxicity — hospitalization required. Cyclosporine or biologics (IL-17/IL-23 inhibitors) for acute management.
- Psoriatic arthritis with erosive joint disease or axial involvement: rheumatology referral for biologic initiation and joint protection strategy.
- Dermatology referral for moderate-severe psoriasis, biologic candidacy, diagnostic uncertainty, or inadequate response to topical therapy.
Apply It · Change One Detail
APPLY IT
A 38-year-old man has well-demarcated silvery plaques on his elbows and knees covering about 5% BSA. He also mentions his fingers have been swollen and painful, especially the tips. The skin disease alone might be managed topically — but the dactylitis and DIP involvement indicate psoriatic arthritis. This patient needs systemic therapy that addresses both skin and joints, and rheumatology co-management.
CHANGE ONE DETAIL
Change one detail — the same patient has no joint symptoms and his plaques cover only 2% BSA with minimal impact on quality of life. This is mild psoriasis. Topical corticosteroids plus calcipotriene is appropriate first-line therapy. Screen for joint symptoms at every visit.
Bottom Line
Skin severity does not predict psoriatic arthritis — screen all psoriasis patients for joint symptoms at every visit. Nail involvement increases PsA risk.
EVIDENCE & REFERENCES
- Menter A, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with biologics. J Am Acad Dermatol. 2019;80(4):1029-1072. doi:10.1016/j.jaad.2018.11.057
- Elmets CA, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with phototherapy. J Am Acad Dermatol. 2019;81(3):775-804. doi:10.1016/j.jaad.2019.04.042