Phenotypes of atopic dermatitis up to 36 months of age by latent class analysis and associated factors in Japan.

Background: Atopic dermatitis (AD) in early childhood is the first allergic manifestation in the atopic march. Recently, latent class analysis (LCA) has revealed the presence of AD subgroups in childhood.

Objective: This study aimed to elucidate different AD phenotypes up to 36 months of age and identify factors associated with a particular AD phenotype in early childhood.

Methods: Pediatric allergists or dermatologists examined children who visited local public health centers in Chiba or Yokohama city at 4, 18, and 36 months of age for regular health checkups between 2003 and 2005. LCA was used to identify AD subtypes on the basis of the course of skin symptoms and comorbidity of other allergic diseases. After LCA, the association between genetic and environmental factors and AD phenotypes was assessed.

Results: A total of 1,378 children who underwent the 3 checkups were included. Complete data were available for 515 children up to 36 months of age. Of 515 children, 183 were diagnosed with AD at least at one out of the 3 time points. The LCA model of these children with AD separated 4 AD phenotypes: early-persistent (EP), early-transient (ET), late-onset (LO), and variable (V). Antibiotic use by 4 months of age was significantly higher in EP group than in other 3 groups. Mother's allergy was significantly higher in EP and LO groups than in other 2 groups. Passive smoking at 18 months of age was higher in LO group than in other groups. Furthermore, >80% of V group was born in spring-summer.

Conclusion: We identified 4 AD phenotypes using LCA on the basis of the onset/course of AD and comorbidity of other allergic diseases and also identified several factors related to the particular phenotypes, which may be useful markers for the prediction of prognosis of AD in early childhood.