What is the best course of treatment for a patient with a dry white patch on the scalp, potentially indicating an underlying fungal or skin condition, such as psoriasis or eczema?

Management of Dry White Patch on Scalp

The most likely diagnosis is seborrheic dermatitis, and first-line treatment should be ketoconazole 2% cream applied twice daily for four weeks, combined with ketoconazole 2% shampoo for scalp involvement. 1, 2, 3

Diagnostic Approach

The differential diagnosis for a dry white patch on the scalp includes:

• Seborrheic dermatitis: Presents with greasy, yellow-white scales, erythema, and commonly affects the scalp 1, 4, 3
• Scalp psoriasis: Shows well-demarcated, indurated plaques with thick silvery scales (not greasy), often with sharper borders than seborrheic dermatitis 5, 1
• Tinea capitis: Fungal infection requiring laboratory confirmation via scalp scraping, hair pluck, or brush sampling for microscopy and culture 5
• Atopic dermatitis: More intense pruritus with lichenification, often with personal/family history of atopy 1

Key distinguishing features: Seborrheic dermatitis typically has greasy, yellow scales versus the thick, silvery scales of psoriasis. Tinea capitis requires laboratory confirmation and presents differently with hair loss patterns. 1, 4

Initial Treatment Algorithm

For Presumed Seborrheic Dermatitis (Most Common):

Step 1: Antifungal therapy (targets Malassezia yeast)

• Ketoconazole 2% cream applied twice daily to affected areas for 4 weeks 2, 3
• Ketoconazole 2% shampoo for scalp involvement, with 88% response rate 1, 3
• Solutions, foams, or shampoos are preferred over ointments/creams for scalp due to hair making traditional formulations messy 1

Step 2: Anti-inflammatory therapy (if significant erythema/inflammation present)

• Low-potency topical corticosteroids (hydrocortisone 1% or prednicarbate 0.02%) for limited periods (2-4 weeks maximum) 1
• Critical caveat: Avoid prolonged corticosteroid use on face/scalp due to risk of skin atrophy, telangiectasia, and tachyphylaxis 1
• For scalp, clobetasol propionate 0.05% shampoo twice weekly can be added if significant inflammation 1

Step 3: Supportive skin care

• Use mild, pH-neutral (pH 5) non-soap cleansers with tepid water 1
• Apply fragrance-free moisturizers after bathing to damp skin 1
• Avoid alcohol-containing preparations as they worsen facial/scalp dryness 1

If Tinea Capitis is Suspected:

Laboratory confirmation is mandatory before treatment 5

• Obtain scalp scraping, hair pluck, or brush sample for KOH microscopy and fungal culture 5
• Oral antifungal therapy is required for tinea capitis; topical therapy alone is insufficient 5
• Selenium sulfide 1% shampoo can reduce transmission but does not cure infection 1

If Scalp Psoriasis is Suspected:

• High-potency topical corticosteroids (clobetasol 0.05% or fluocinonide 0.05%) in solution form for scalp 5
• Topical vitamin D analogs (calcipotriene/calcitriol) 5
• Coal tar preparations (1% strength) to reduce inflammation and scaling 5, 1

When to Refer to Dermatology

Referral is indicated for: 1

• Diagnostic uncertainty or atypical presentation
• Failure to respond after 4 weeks of appropriate first-line therapy
• Recurrent severe flares despite optimal maintenance therapy
• Need for second-line treatments or systemic therapy

Common Pitfalls to Avoid

• Do not undertreat due to fear of corticosteroid side effects; use appropriate potency for adequate duration, then taper 1
• Do not use corticosteroids long-term on face/scalp (>2-4 weeks) due to atrophy and tachyphylaxis risk 1
• Do not confuse persistent itching after treatment with treatment failure; mild burning/itching from inflammation can persist for days after yeast elimination 1
• Do not use topical therapy alone for tinea capitis; oral antifungals are mandatory 5
• Avoid greasy or occlusive products that can promote folliculitis 1
• Watch for secondary bacterial infection (crusting, weeping, pustules) requiring oral antibiotics like flucloxacillin 1

Maintenance Therapy

After initial clearance with ketoconazole 2% cream: 1

• Taper to once daily application
• Consider switching to ketoconazole shampoo for long-term scalp maintenance
• Continue supportive skin care measures indefinitely