What is the diagnosis and treatment for a patient presenting with red raised skin irritants and white scales, possibly indicative of a condition such as psoriasis, eczema, or contact dermatitis?

Diagnosis: Psoriasis

The clinical presentation of red raised skin lesions with white scales is most consistent with psoriasis vulgaris, which classically presents as well-demarcated, red plaques with silvery scale. 1

Diagnostic Approach

Key distinguishing features to confirm psoriasis:

• Well-demarcated, indurated plaques with thick silvery scale (rather than the greasy, yellow scales typical of seborrheic dermatitis) 1, 2
• Sharp borders and thicker plaques compared to the less defined borders seen in eczematous conditions 2
• Common locations: scalp, elbows, knees, and presacral region, though any area may be involved 1
• Personal or family history of psoriasis strongly supports the diagnosis 2

Critical differential diagnoses to exclude:

• Atopic dermatitis: presents with more intense pruritus, lichenification in chronic cases, and flexural involvement rather than extensor surfaces 1, 2
• Seborrheic dermatitis: characterized by greasy, yellow scales (not white/silvery), typically affects scalp, face, and intertriginous areas 2
• Contact dermatitis: shows sharp demarcation corresponding to contact area, requires patch testing if suspected 2, 3
• Cutaneous T-cell lymphoma: consider if refractory to standard treatment; requires biopsy showing atypical lymphocytes 2

When biopsy is indicated: If diagnosis is uncertain after clinical examination, or if the condition fails to respond to appropriate first-line therapy after 4 weeks 1, 2

Treatment Algorithm

Mild Psoriasis (BSA <3%)

First-line topical therapy:

• Topical corticosteroids of appropriate potency are the cornerstone of initial management 1
• Grade III (moderately potent) preparations: no more than 100g per month with regular clinical review 1
• Avoid unsupervised repeat prescriptions and ensure periods each year when alternative treatments are employed 1
• Alternative topical agents: tar preparations and dithranol have proven efficacy 1

Important safety considerations:

• Grade I (very potent) or Grade II (potent) corticosteroids should only be used under dermatological supervision 1
• Avoid long-term continuous use on the face beyond 2-4 weeks due to risk of skin atrophy, telangiectasia, and tachyphylaxis 2

Moderate to Severe Psoriasis (BSA >3% or significant impact on quality of life)

Phototherapy options:

• Multiple forms are beneficial: narrow-band UVB (NB-UVB), broad-band UVB (BB-UVB), UVA, PUVA, and Goeckerman therapy 1
• Indicated after failure of topical therapies including emollients, topical anti-inflammatory agents, and environmental modifications 1
• Avoid applying moisturizers immediately before phototherapy as they create a bolus effect 2

Systemic immunomodulatory agents:

• Reserved for patients in whom optimized topical regimens and/or phototherapy do not adequately control disease 1
• Methotrexate: indicated for severe, recalcitrant, disabling psoriasis not adequately responsive to other therapies, only after biopsy confirmation and dermatologic consultation 4
• Cyclosporine: requires careful monitoring with baseline and regular assessment of blood pressure, serum creatinine, CBC, and liver function 5
• Patients requiring systemic agents should be under continuing supervision of a consultant dermatologist due to potential toxicity 1

Essential Supportive Care

Skin barrier maintenance:

• Use mild, pH-neutral (pH 5) non-soap cleansers or dispersible creams as soap substitutes to preserve natural lipid barrier 2
• Apply fragrance-free moisturizers containing petrolatum or mineral oil immediately after bathing to damp skin 2
• Avoid hot water (use tepid water instead) as temperatures above 40°C damage the skin barrier 2, 3

Medications to avoid:

• Beta-blockers, NSAIDs, lithium, chloroquine, and mepacrine may precipitate or worsen psoriasis, with lithium and antimalarials potentially causing severe deterioration 1
• Alcohol consumption is thought to worsen psoriasis 1

Common Pitfalls

• Undertreatment due to fear of corticosteroid side effects: use appropriate potency for adequate duration, then taper 2
• Failure to try alternative topical agents: some patients who fail one agent will respond to another before requiring more aggressive management 1
• Missing allergic contact dermatitis: 35% of patients with psoriasis may have concomitant allergic contact dermatitis requiring patch testing 6
• Overlooking cutaneous T-cell lymphoma: if refractory to standard treatment, biopsy is essential 2

When to Refer to Dermatology

Immediate referral indicated for:

• Diagnostic uncertainty or atypical presentation 2
• Failure to respond after 4 weeks of appropriate first-line therapy 2
• Need for systemic immunomodulatory agents 1
• Suspected malignancy or cutaneous T-cell lymphoma 2
• Severe psoriasis requiring specialized management 1