Lower Serum Interleukin-33 Levels in Infantile Atopic Dermatitis

It is crucial to understand the pathophysiology of infantile atopic dermatitis (AD)for the management of subsequent allergic diseases. Cytokines like IL-33 play a role in causing Th2/Th1 imbalance. While IL-33 levels increase in adult AD patients, it remains unclear if this occurs in infantile AD.

A study that involved 10 infants diagnosed with AD according to the American Academy of Dermatology(AAD) guidelines. The investigative tests included peripheral eosinophil count, thymus and activation-regulated chemokine (TARC), non-specific IgE, house-dust mite (HDM)-specific IgE antibody, and egg white (EW)-specific antibody levels. The serum IL-33 level was measured using an enzyme-linked immunosorbent assay.

At the time of diagnosis –median ageof 4 months, peripheral eosinophil count was 493/µL, TARC was 5299 pg/mL, and total non-specific IgE was 24.4 IU/mL. HDM and EW sensitizations were observed in one and seven patients, respectively. Serum IL-33 levels (1.32–2.49 pg/mL) were not elevated in any patient.

Therefore, none of the patients had increased serum IL-33 levels; however, the TARC levels were elevated in all cases. This suggests that serum IL-33 may not rise in early-onset infantile AD. IL-33 might exert significant local skin effects only in this context, with increased levels potentially requiring barrier dysfunction and epidermal cell damage from prolonged aggressive scratching.

Of note, infants do not scratch as intensely as older individuals and the pathophysiology of infantile AD may differ from that of adult AD. This aligns with Tamagawa-Mineoka et al.'s findings of higher IL-33 levels in AD patients with numerous excoriations.

Source: Fujita Y, Yoshihara S. Indian Journal of Pediatrics. 2023 Oct 28:1-.