What are the treatment options for patients with psoriasis and seborrheic dermatitis?

Treatment of Psoriasis and Seborrheic Dermatitis

For patients with both psoriasis and seborrheic dermatitis affecting the scalp, initiate combination therapy with clobetasol propionate 0.05% shampoo applied twice weekly (leaving on scalp 5-10 minutes before rinsing) alternating with ketoconazole 2% shampoo twice weekly for 4 weeks, followed by maintenance with ketoconazole once weekly. 1

Initial Treatment Algorithm

For Scalp Involvement (Most Common Overlap Site)

Week 1-4 (Active Treatment Phase):

• Apply clobetasol propionate 0.05% shampoo on days 1 and 4 of each week, leaving on scalp for 5-10 minutes before rinsing to address the psoriatic inflammation 1, 2
• Apply ketoconazole 2% shampoo on days 2 and 5 of each week, leaving on for 5 minutes before rinsing to target the Malassezia component of seborrheic dermatitis 1, 3
• Apply emollients 1-3 times daily between shampoo treatments to reduce scaling and maintain skin barrier function 1
• This combination regimen demonstrates significantly greater efficacy than either agent alone, with rapid symptom relief within 3-4 weeks 1, 2

After Week 4 (Maintenance Phase):

• Discontinue clobetasol after 4 weeks maximum to avoid skin atrophy, striae, telangiectasia, and HPA axis suppression 1, 4
• Transition to ketoconazole 2% shampoo once weekly to sustain remission and prevent relapse 1
• Continue emollients as needed 1

For Facial and Body Involvement

When psoriatic plaques predominate:

• Apply moderate-to-high potency topical corticosteroid (betamethasone dipropionate 0.05% or equivalent) twice daily for 2-4 weeks maximum 5, 6
• Add calcipotriol (vitamin D analog) on non-corticosteroid days if psoriatic plaques are prominent, as this provides synergistic effect 1, 6
• For face and intertriginous areas, use low potency corticosteroids (class 5-7) or tacrolimus 0.1% to minimize atrophy risk 5, 6

When seborrheic dermatitis predominates:

• Apply ketoconazole 2% cream twice daily for 4 weeks to affected areas 3
• May combine with low-potency corticosteroid if significant inflammation present 7

For mixed presentations (sebopsoriasis):

• Tacalcitol (vitamin D3 analog) cream applied twice daily for 4 weeks has demonstrated complete clearance of facial eruptions in patients with sebopsoriasis, with sustained effect for 2 months after discontinuation 8
• This avoids the atrophy risk of prolonged corticosteroid use on the face 8

Critical Monitoring Requirements

• Review patients clinically every 4 weeks during active treatment to assess response and monitor for adverse effects 1, 5, 6
• No unsupervised repeat prescriptions of high-potency corticosteroids 9, 5, 6
• Maximum 100g of moderate-potency corticosteroid per month 9, 5, 6
• Plan annual periods using alternative non-corticosteroid treatments to prevent continuous high-potency steroid exposure 9, 5, 6

Common Pitfalls and How to Avoid Them

Abrupt corticosteroid withdrawal:

• Taper frequency gradually after clinical improvement rather than stopping abruptly to prevent rebound flare phenomenon 5
• In rare instances, withdrawal of corticosteroid treatment in psoriasis can precipitate pustular psoriasis 4

Systemic corticosteroid use:

• Never use systemic corticosteroids for psoriasis, as they can precipitate severe psoriasis flares (including pustular or erythrodermic forms) upon discontinuation 1, 6

Medication interactions:

• Avoid medications that worsen psoriasis: lithium, chloroquine, beta-blockers, and NSAIDs 9, 1, 6
• These can cause severe, potentially life-threatening deterioration of psoriasis 9

Misdiagnosis of treatment failure:

• Perceived "tachyphylaxis" to topical corticosteroids is often due to poor patient adherence rather than receptor down-regulation 6
• Before escalating therapy, verify proper application technique and adherence 6

Alternative Second-Line Options

For localized thick plaques not responding to initial therapy:

• Intralesional triamcinolone acetonide (up to 20 mg/mL every 3-4 weeks) for non-responding thick plaques 1, 5
• Calcineurin inhibitors (tacrolimus 0.1%, pimecrolimus) as steroid-sparing agents for prolonged use, particularly useful for facial/intertriginous extension 1, 5

For scalp involvement:

• Coal tar preparations (0.5-1.0% crude coal tar in petroleum jelly, increasing to maximum 10%) can be used as alternative to corticosteroids, though cosmetically less elegant 9, 6
• Anthralin (dithranol) 0.1-0.25% increasing in doubling concentrations, though limited by staining and irritation 9

Escalation Criteria to Dermatology

Refer to dermatology when:

• Body surface area involvement exceeds 5% 5, 6
• Inadequate response to optimized topical therapy after 8 weeks 5
• Scalp tenderness persists despite adequate anti-inflammatory treatment 1, 5
• Signs of erythrodermic or pustular psoriasis develop (medical emergency) 9, 1, 5
• Consideration of systemic therapy (methotrexate, acitretin, cyclosporine, biologics, or phototherapy) 9, 5

Special Considerations

For patients planning pregnancy:

• All systemic agents for psoriasis are absolutely contraindicated in pregnancy 9
• Topical treatments remain first-line, with careful selection of pregnancy-compatible options 9

For guttate presentations:

• Use lower concentrations of tar and dithranol as erupting lesions are less tolerant of topical treatment 5
• Consider UVB phototherapy as especially helpful for guttate presentations 5
• Investigate and treat streptococcal infection with phenoxymethylpenicillin or erythromycin if evidence of persistent infection 5