Objective:

To evaluate the prevalence, clinical characteristics, and temporal relationships of autoimmune diseases in children and adolescents with type 1 diabetes mellitus (T1D), and to identify factors associated with their occurrence.

Approach:

• Study Design: Retrospective study including 639 children and adolescents with T1D followed at a tertiary pediatric endocrinology center from January 2004 to October 2018.
• Data Collection: Demographic, clinical, laboratory, and autoantibody data were reviewed; autoimmune diseases identified through routine screening and clinical follow-up.
• Statistical Analysis: Multivariable logistic regression was used to assess factors associated with additional autoimmune diseases.

Key Findings:

• 18.8% of subjects with T1D had at least one additional autoimmune disease.
• Most frequent comorbidities were autoimmune thyroiditis (AIT, 12.7%) and celiac disease (CD, 5.9%), followed by vitiligo (1.3%), autoimmune gastritis/pernicious anemia (0.15%), and autoimmune hepatitis (0.15%).
• Female sex was independently associated with the presence of additional autoimmune diseases (OR = 1.61).
• Most autoimmune diseases were diagnosed concurrently with or after T1D onset, clustering within the first two years.

Interpretation:

Age at diagnosis of T1D was positively correlated with the age at diagnosis of AIT and CD, indicating a shorter interval between T1D onset and these autoimmune diseases in older patients.

Limitations:

• The study was retrospective and relied on medical records, which may have incomplete data.
• Not all autoimmune comorbidities, including Addison’s disease, autoimmune gastritis/pernicious anemia, autoimmune hepatitis, and vitiligo, were systematically screened annually.

Conclusion:

Autoimmune comorbidities, particularly AIT and CD, are common in pediatric T1D, with most diagnoses occurring within the first two years around diabetes onset.