What is the management approach for localized pustular psoriasis?

Management of Localized Pustular Psoriasis

For localized pustular psoriasis of the palms and soles, start with moderately potent topical corticosteroids (British National Formulary grade III) as first-line therapy, with topical coal tar and dithranol as alternative options, while avoiding systemic corticosteroids due to risk of disease exacerbation. 1

First-Line Topical Therapy

Topical Corticosteroids

• Moderately potent topical corticosteroids (grade III) provide symptom relief and are the recommended initial treatment 1, 2
• A hydrocolloid occlusive dressing (such as Actiderm) applied over triamcinolone acetonide 0.1% cream every third day demonstrates superior efficacy compared to clobetasol propionate 0.05% cream applied twice daily, achieving complete clearance in 63% versus 21% of patients 3
• Clobetasol propionate, while highly potent, carries risks of HPA axis suppression at doses as low as 2g per day and may paradoxically exacerbate pustular psoriasis upon withdrawal 4

Alternative Topical Agents

• Topical coal tar (starting at 0.5-1.0% crude coal tar in petroleum jelly, increasing to maximum 10%) provides some benefit, with cruder extracts being more effective than refined products 1
• Topical dithranol (anthralin) may be beneficial, starting at 0.1-0.25% concentration and increasing in doubling concentrations as tolerated, though great care is needed on sensitive areas 1

Systemic Treatment Options

When to Consider Systemic Therapy

Treatment is generally unsatisfactory with topicals alone for localized pustular psoriasis, necessitating consideration of systemic agents in refractory cases 1

Systemic Agent Selection

• Acitretin (0.1-1 mg/kg/day) has achieved some success in localized pustular psoriasis and is particularly effective for pustular variants 1, 2
• PUVA (psoralens plus ultraviolet A) is considered the systemic treatment of first choice with the least toxicity among systemic options 2
• Infliximab 5 mg/kg demonstrates rapid efficacy in severe cases, though it is primarily indicated for generalized pustular psoriasis 2, 5

Critical Contraindications for Systemic Agents

• All systemic agents are absolutely contraindicated in pregnancy and require mandatory contraception counseling before initiation 2, 6
• Acitretin is contraindicated in women planning pregnancy within 2 years of stopping treatment 2, 6
• Cyclosporine is contraindicated with abnormal renal function or uncontrolled hypertension 2, 6
• Methotrexate is contraindicated in pregnancy, breastfeeding, significant hepatic damage, and blood disorders 2, 6

Phototherapy Considerations

• Ultraviolet B radiation may be helpful but must be used with extreme caution as it may exacerbate pustular psoriasis 2
• PUVA requires starting dose determination after estimation of minimum phototoxic dose at 72 hours, with 70% of this dose as the initial treatment 1
• Commercially available sunbeds (emitting ultraviolet A) are rarely effective and not recommended due to side effects including premature skin aging 1

Critical Pitfalls to Avoid

Systemic Corticosteroids

• Never use systemic corticosteroids as primary therapy for pustular psoriasis, as they precipitate severe disease flares upon discontinuation and can trigger generalized pustular psoriasis or erythrodermic psoriasis 2, 6, 7
• In rare instances, treatment or withdrawal of corticosteroids is thought to have exacerbated the disease or provoked the pustular form 4

TNF Antagonist Caution

• TNF antagonists (infliximab, etanercept, adalimumab) should be avoided in chronic palmoplantar pustulosis, as they may exacerbate this specific condition 2, 6
• However, these agents may be reasonable for acropustulosis if it has major quality of life impact 2

Medication-Induced Exacerbations

• Lithium, chloroquine, and mepacrine may cause severe deterioration of pustular psoriasis 5, 6
• Beta-blockers and NSAIDs may worsen psoriasis in some patients 5

Monitoring Requirements

For patients on systemic therapy, pretreatment assessment must include history, examination, full blood count, liver function tests, and serum creatinine 6

Regular ongoing monitoring requirements depend on the specific agent:

• Acitretin: liver function tests and fasting serum lipids 6
• Cyclosporine: blood pressure and serum creatinine monitoring 6
• Methotrexate: full blood count and liver function tests regularly 6