Codes

Look For

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

• Nummular dermatitis – Intensely pruritic, coin-shaped lesions almost exclusively seen on the extremities.
• Tinea corporis – Usually fewer isolated lesions. Check potassium hydroxide (KOH) prep.
• Tinea versicolor – Less scale and less inflammatory. KOH-positive.
• Pityriasis rosea – Look for a herald patch, collarette of scale, and orientation of lesions (fir-tree pattern in skin tension lines).
• Small plaque parapsoriasis – More common in older adults; chronic asymptomatic patches.
• Pityriasis lichenoides chronica – Biopsy will assist in differentiating from guttate psoriasis, predominantly CD8+ T-cell infiltrate.
• Lymphomatoid papulosis – Biopsy will assist in differentiating from guttate psoriasis, predominantly CD30+ T-cell infiltrate. Generally presents as recurrent crops of papules. Uncommon in children.
• Psoriasiform drug eruption – Ask about medication history.
• Viral exanthem – Usually less scaly.
• Chronic papular atopic dermatitis
• Pityriasis lichenoides et varioliformis acuta (PLEVA) presents with recurrent crops of crusted, vesicular, or pustular lesions.

Best Tests

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Management Pearls

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Therapy

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References

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