What is the diagnosis and treatment for a 6-year-old male with a red raised area on the scalp with pustules and no significant past medical history?

Diagnosis and Treatment of Red Raised Scalp Area with Pustules in a 6-Year-Old Male

Most Likely Diagnosis

This presentation is most consistent with pustular psoriasis of the scalp, though kerion (severe tinea capitis with secondary bacterial infection) and eosinophilic pustulosis of the scalp must be ruled out. 1, 2, 3

Diagnostic Approach

Key Clinical Features to Assess

• Distribution pattern: Pustular psoriasis typically involves the scalp with well-demarcated, raised erythematous plaques with pustules, while kerion presents as a boggy, tender mass with purulent drainage 4, 3
• Associated findings: Look for psoriatic plaques elsewhere on the body (elbows, knees, presacral region), nail pitting, or oil-drop sign which strongly suggest psoriasis 4
• Pruritus severity: Eosinophilic pustulosis presents with intense pruritus and primarily affects the scalp in young children 2
• Fever or systemic symptoms: Generalized pustular psoriasis (von Zumbusch variant) presents with fever and toxicity, requiring urgent intervention 4

Diagnostic Testing

• KOH preparation and fungal culture: Essential to rule out tinea capitis with kerion formation 3
• Bacterial culture: If secondary infection is suspected 2
• Skin biopsy: Shows neutrophils in stratum corneum for pustular psoriasis; dermal eosinophilia for eosinophilic pustulosis 4, 2

Treatment Algorithm

For Localized Pustular Psoriasis (Most Common Scenario)

First-line therapy should be topical calcineurin inhibitors (tacrolimus 0.1% ointment) for scalp involvement, as this achieves excellent improvement within 30 days without risk of skin atrophy. 1, 5

• Alternative first-line: Combination calcipotriol/betamethasone dipropionate suspension once daily for up to 8 weeks achieves disease clearance in 58% of pediatric patients aged 12-17 years 5
• For younger children (<12 years): Use moderately potent (Class III) topical corticosteroids for body lesions, but avoid high-potency steroids due to HPA axis suppression risk from elevated body surface area-to-volume ratio 1, 5

For Severe, Unstable, or Generalized Pustular Psoriasis

Acitretin 0.1-1 mg/kg/day is the first-line systemic therapy, with response typically seen within 3 weeks. 1, 6

• Mechanism: Acitretin shows particularly rapid responses in pustular psoriasis by inhibiting neutrophil chemotaxis and reducing keratinocyte hyperproliferation 4, 6
• Combination approach: Acitretin combined with narrowband UVB phototherapy is synergistic and allows dose reduction of both agents 1, 6
• Alternative for crisis management: Cyclosporine 2-5 mg/kg/day achieves skin clearance in approximately 4 weeks and is excellent for rapidly progressive disease 1

For Refractory or Life-Threatening Disease

Infliximab 5 mg/kg IV at weeks 0,2, and 6, then every 8 weeks is recommended for severe pustular psoriasis unresponsive to other systemic medications. 1, 6

Critical Safety Considerations

Age-Specific Precautions

• Children 0-6 years: Extreme caution with topical corticosteroids due to high risk of HPA axis suppression from elevated body surface area-to-volume ratio 1, 5
• Prescribe limited quantities with clear application instructions to prevent overuse 1, 5

Medication-Specific Warnings

• Acitretin: Absolute contraindication in female adolescents approaching childbearing potential, as it remains stored in the body for up to 3 years when reverse-esterified to etretinate in the presence of alcohol 1, 6
• Systemic therapy monitoring: Routine clinical and laboratory monitoring is mandatory during treatment with acitretin, cyclosporine, or biologics 1

Common Pitfalls to Avoid

• Misdiagnosis as bacterial infection: Pustular psoriasis is sterile; avoid prolonged antibiotic therapy without culture confirmation 2
• Abrupt discontinuation of topical steroids: This causes rebound flares; gradual tapering is essential 5
• Overlooking systemic involvement: Screen for psoriatic arthritis, metabolic syndrome, and inflammatory bowel disease in children with psoriasis 4
• Inadequate monitoring: Failure to monitor vitamin D metabolites when using calcipotriol on large body surface areas can lead to hypercalcemia 5

Alternative Diagnoses to Consider

If Kerion (Tinea Capitis with Secondary Infection)

• Requires systemic antifungal therapy (griseofulvin or terbinafine) plus antibiotics if bacterial superinfection is confirmed 3

If Eosinophilic Pustulosis of the Scalp

• Self-limited condition relieved by topical steroids; dapsone may be beneficial in refractory cases 2
• Characterized by transient blood eosinophilia and dermal eosinophilia on biopsy 2