Dystrophin genetic variants and autism

**Background:** Autism spectrum disorder (ASD) is a neurodevelopmental disorder affecting approximately 1% of the population, with a strong genetic component. Loss-of-function variants in the dystrophin gene (DMD) are a well-known cause of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). While intellectual disability has long been associated with dystrophinopathies, the link with ASD is more recent. This review examines the prevalence of ASD in DMD/BMD patients, the role of dystrophin isoforms, and the contribution of genetic background to ASD in these individuals. The authors also present four new families with ASD and dystrophin variants.

**Methods:** The authors conducted a literature review of studies evaluating ASD prevalence in DMD/BMD cohorts, focusing on genotype-phenotype correlations. They also describe six ASD individuals from four unrelated families identified at their center. Whole exome sequencing (WES) was performed in two families (F1 and F2) from a cohort of 328 ASD individuals (65 females, 263 males). The other two families (F3 and F4) were identified from a neuromuscular cohort. Dystrophin variants were classified according to ACMG guidelines. ASD diagnosis was confirmed using standardized tools such as the Childhood Autism Rating Scale (CARS) and ADOS-2.

**Key Results:** The literature review identified 19 studies reporting ASD prevalence in dystrophinopathies, with rates ranging from 0% to 21% in DMD and 0% to 11.4% in BMD. Prospective studies using formal ASD evaluations (e.g., ADOS) reported higher frequencies (3.8–21%) compared to studies based on medical records (0–11%). In the authors' cohort, two dystrophin variants were identified among 328 ASD individuals (0.61%), significantly higher than the general population DMD prevalence (~1:7000–10,000). The four families included: (1) Discordant monozygotic twins (P1 with ASD, P2 without) carrying an out-of-frame deletion of exons 2–9; (2) A 5-year-old male (P3) with high-functioning ASD and a stop-gain variant in exon 78 (c.11017A>T, p.Arg3673*); (3) Non-identical triplets (P4, P5, P6) all with ASD, with two (P4, P5) having DMD due to a deletion (c.64_69+16del) and one (P6) without DMD; (4) Monozygotic twins (P7, P8) with DMD and ASD, carrying a stop-gain variant in exon 14 (c.1591C>T, p.Arg531*) and a pathogenic variant in EBF3 (c.616C>T, p.Arg206*). WES in these families revealed additional rare variants in ASD-related genes (e.g., CSF1R, SQSTM1, SPEN, CHD3, NRXN1) and a de novo variant in SV2A in the non-DMD triplet.

**Clinical Implications:** The findings confirm that ASD is a relevant comorbidity in dystrophinopathies, with prevalence estimates varying widely due to methodological differences. Standardized diagnostic guidelines are needed. Genotype-phenotype correlations suggest that both long and short dystrophin isoforms (including Dp140 and Dp71) may contribute to ASD risk, but the genetic background plays a crucial role. Severe ASD in DMD/BMD patients may result from the co-occurrence of multiple monogenic disorders (e.g., DMD and EBF3 variants) or an oligogenic/polygenic model. Rare dystrophin variants with greater impact on the brain than muscle may be enriched in ASD cohorts. Early ASD diagnosis is essential for optimal management, especially given increased longevity in DMD patients. The authors advocate for consortia to investigate the genetic architecture of ASD in dystrophinopathies and for functional studies using iPSC and CRISPR-Cas9 models.