An 8-Year-Old Boy with Scaly Papules on the Knees and Elbows

Differential Diagnosis

• Keratosis pilaris
• Pityriasis rubra pilaris
• Lichen spinulosus
• Atopic dermatitis

Diagnosis

This patient was diagnosed with lichen spinulosus, a rare and benign cutaneous disorder characterized by sudden onset of localized circumscribed plaques comprised of follicular hyperkeratotic papules. It most frequently occurs in children and adolescents; however, young adults can also be affected.

Learnings/What to Look for

• Etiology and pathogenesis are not known, although atopic, infectious, and genetic factors have been proposed as causes
• Patients often have a history of atopy
• Although usually localized to certain sites of predilection, a more severe generalized variant of lichen spinulosus also exists. It occurs in association with nodulocystic acne and pityriasis rubra pilaris as part of type VI (HIV-associated) pityriasis rubra pilaris
• Rare associations include Crohn’s disease, Hodgkin’s disease, seborrheic dermatitis, syphilis, id reactions to fungal infections, and heavy metal ingestions
  • Note that these associations are 1) not causal relationships and 2) may be the consequence of ascertainment bias

Pearls for Urgent Care Management

• Lichen spinulosus has a variable course. Most cases tend to resolve spontaneously at puberty, although persistent cases have also been described
• While no treatment is required, effective therapeutic options include topical keratolytic agents and topical retinoids

Acknowledgment: Images and case presented by VisualDx (www.VisualDx.com/JUCM).