Genetic Diagnosis and Identification of a Novel De Novo RELA Variant in Familial Behçet-like Autoinflammatory Syndrome Type 3: A Case Report

To perform genetic diagnosis and pedigree analysis in a case of autosomal dominant Familial Behçet-like Autoinflammatory Syndrome type 3 (AIFBL3) caused by a novel RELA variant. Peripheral blood samples collected from the proband and parents underwent conventional genetic screening, next-generation sequencing (NGS), and Sanger sequencing for familial validation. A de novo heterozygous RELA variant (NM₀21975. 4: c. 539 C > T, p. Ser180Phe) was identified in the proband. Parental testing confirmed its de novo origin. The RELA c. 539 C > T variant was classified as likely pathogenic for AIFBL3, providing a basis for genetic counseling. In future pregnancies, prenatal diagnosis through targeted familial mutation analysis could be offered to this family to inform reproductive decision-making. New RELA variant found: De novo c. 539 C > T (p. Ser180Phe) in the proband. Diagnosis confirmed: Likely pathogenic for AIFBL3. De novo origin: Not inherited from parents. Clinical use: Supports genetic counseling and informs the option of targeted prenatal diagnosis.