Interleukin-1 Polymorphisms in Caucasian Adults with Down Syndrome and Advanced Periodontitis: A Cross-Sectional Study

Background/Objectives: Down syndrome (DS) is characterised by a marked susceptibility to early-onset severe periodontitis, suggesting an intrinsic host predisposition. Interleukin-1 (IL-1) gene variants may influence inflammatory burden, yet DS-specific evidence is limited. Methods: Nineteen Caucasian adults with DS underwent a comprehensive periodontal examination and received a periodontal diagnosis according to the AAP/EFP 2018 classification. Buccal swabs were genotyped by real-time PCR for IL1A −889, IL1B +3954 and IL1RN +2018; the composite IL1A/B genotype was also evaluated. Results: All participants presented advanced, generalized periodontitis (Stage III/IV: 37%/63%; Grade B/C: 32%/68%). Variant alleles were detected in 63% for IL1A, 53% for IL1B and 37% for IL1RN, and the composite IL-1A/B genotype in 47%. Variant carriage showed associations with higher Clinical Attachment Loss (IL1A p = 0.03; IL1B p = 0.002; composite p = 0.012) and Bleeding on Probing (IL1A p = 0.02; IL1RN p = 0.05; composite p = 0.04). The composite genotype was associated with Stage IV (p = 0.027) and Grade C (p = 0.005), and tooth loss was greater among variant carriers for all polymorphisms (p = 0.