Atopic Dermatitis

• Figure 2.7 A: Pityriasis alba (Courtesy of Dr. Paul Getz) B: Molluscum contagiosum

  Occurs in 10–15% children, often presenting at 2–3 months of age; multifactorial pathogenesis but includes ↑ secretion of T_H2 cytokines (IL-4, IL-5)
• Triad of atopy: AD, allergic rhinitis, asthma
• Few may have allergy to specific foods, which may exacerbate AD (eggs, milk, soybeans, fish, wheat, peanuts)
• Presents with eczematous lesions, xerosis, and lichenification
• Distribution varies with age
  • Infants: face, scalp, and extensors
  • Children: antecubital/popliteal fossae, neck, wrists, ankles
  • Adults: typically hands (chronic hand eczema)
  
  

  Atopic patients with ↓ amount of innate antimicrobial peptides: human β-defensins (HBD) and cathelicidins (LL37)

  
  
• Pityriasis alba: hypopigmented patches with minimal scale; may be only manifestation of AD (Figure 2.7A)
• Complications: keratoconus (conical deformity of cornea), eyelid dermatitis, ↑ risk of infection (impetigo, eczema herpeticum, molluscum contagiosum) (Figure 2.7B)
• Treatment: topical corticosteroid, topical calcineurin inhibitor, oral corticosteroid (short course), oral antihistamine, phototherapy