Mucous Stools in Infancy as an Early Marker of the Atopic March: A Four-Year Cohort Study of Respiratory Atopy Risk

<b>Background:</b> Mucous stools in infancy are commonly attributed to non-IgE-mediated gastrointestinal food allergies and are generally considered transient and benign. However, whether mucous stools may indicate an atopy-prone clinical phenotype and relate to later respiratory atopy remains insufficiently explored. <b>Objective:</b> To evaluate the long-term risk of respiratory atopy (asthma and/or allergic rhinitis) in infants presenting with mucous stools during the first year of life and to identify early clinical predictors of this risk. <b>Methods:</b> This retrospective cohort study included infants who presented with mucous stools within the first 12 months of life and were followed for four years. Baseline demographic, clinical, dietary, and laboratory data were extracted from standardized medical records. Mucus severity was graded using a pragmatic 0-3 clinical mucus score. The primary outcome was physician-diagnosed asthma and/or allergic rhinitis at four years. Multivariable logistic regression was used to identify independent predictors, with model discrimination assessed by the area under the receiver operating characteristic curve (AUC). <b>Results:</b> A total of 142 infants with complete follow-up data were analyzed. At four years, respiratory atopy was observed in 45 infants (31.7%). In multivariable analysis, family history of atopy (adjusted odds ratio [aOR] 2.68, 95% CI 1.20-5.98, <i>p</i> = 0.016) and wheezing at presentation (aOR 3.74, 95% CI 1.56-8.94, <i>p</i> = 0.003) were independent predictors of respiratory atopy. The mucus score was associated with respiratory atopy in univariable analysis but did not remain an independent predictor in multivariable modeling. The model showed good discrimination (AUC = 0.769). <b>Conclusions:</b> In this cohort of infants presenting with mucous stools in the first year of life, respiratory atopy was observed in nearly one-third by age 4. While mucous stool burden was associated with the outcome in univariable analyses, it did not remain an independent predictor after adjustment. Early wheezing and a family history of atopy were the strongest clinical predictors and may help identify infants who warrant closer follow-up. These findings should be interpreted as associative and hypothesis-generating in the absence of a mucous-stool-free comparison group.