Synopsis
Assess three high-impact psoriasis sites, separate common mimics, collect specimens before masking infection, and match formulation, potency and referral to anatomy and functional burden.
- Scalp psoriasis forms sharply defined plaques with adherent scale, often extending beyond the hairline; part the hair and inspect ears, face, elbows and nails before deciding it is simple dandruff.
- Nail matrix disease causes pitting, ridging or crumbling; nail-bed disease produces salmon or oil-drop change, onycholysis and subungual hyperkeratosis.
- Palmoplantar plaques are thick, sharply bounded and fissured; palmoplantar pustulosis produces recurrent sterile pustules that become yellow-brown and is strongly associated with smoking.
- Difficult-site severity is measured by pain, walking, hand use, sleep, work, appearance and distress, not by body surface area alone.
- For scalp psoriasis, NICE starts with a potent topical corticosteroid once daily for up to four weeks, then checks technique, formulation and scale before changing therapy.
- Do not prescribe oral antifungal treatment for a dystrophic nail without adequate microscopy and culture or another validated fungal test; psoriasis and fungus may coexist.
- Major nail impact, uncontrolled palmoplantar disease or failure of properly used topical therapy merits dermatology referral and may meet criteria for phototherapy or systemic treatment.
- Ask about joint, heel, digit and back symptoms: nail psoriasis increases suspicion, but skin or nail severity does not determine arthritis severity.
Key red flags
Painful fluctuant swelling, spreading warmth, purulent discharge or fever suggests bacterial infection and requires prompt severity and sepsis assessment.
Rapidly progressive nail destruction, scarring scalp alopecia or an ulcerated palmoplantar lesion needs expedited diagnostic review because permanent loss or malignancy is possible.
New generalised pustules, malaise or extensive skin inflammation requires same-day dermatology assessment rather than topical escalation.
Dactylitis, joint swelling, heel pain or inflammatory back pain may accompany nail psoriasis and should trigger rheumatology referral when psoriatic arthritis is suspected.
Rapid nail loss, scarring hair loss, severe fissuring that prevents walking or a changing ulcerated acral lesion needs accelerated assessment rather than repeated empirical topical treatment.
Investigation priorities
Map scalp, nail-unit, palm and sole morphology and search for psoriasis at less symptomatic sites.
Management branches
Confirmed scalp psoriasis without infection or scarring alopecia.
- Part the hair, loosen thick adherent scale with salicylic-acid, oil or emollient preparation where appropriate, then wash out gently rather than picking plaques.
- Apply a potent topical corticosteroid scalp formulation once daily for up to four weeks, directing it onto skin rather than coating hair.
- At four weeks, check quantity, technique and acceptability; if response is inadequate, try another potent-steroid formulation and/or deliberate descaling before assuming pharmacological failure.
- After a further inadequate four-week approach, NICE offers once-daily calcipotriol/betamethasone combination for up to four weeks, or once-daily vitamin-D analogue for mild-to-moderate disease when steroid cannot be used.