A retrospective evaluation of patients diagnosed with autism spectrum disorder in terms of underlying genetic causes who applied to Hacettepe University İhsan Doğramaci children's Hospital pediatric genetics department outpatient clinic, hacettepe university faculty of medicine, department of pediatrics

Autism spectrum disorder is a neurodevelopmental disorder characterized by deficits in social communication, along with restricted, repetitive behaviors, interests, and activities. Autism has a heterogeneous etiology showing polygenic inheritance and being influenced by various environmental factors. Currently, the genetic etiology can be identified in about 10-25% of patients. In this study, the demographic characteristics, parental ages during gestation, and the presence of minor dysmorphic features, structural anomalies, and accompanying comorbidities along with the results of genetic tests of 260 patients diagnosed with autism spectrum disorder who applied to Hacettepe University İhsan Doğramacı Children's Hospital Pediatric Genetics Outpatient Clinic between the dates January 01, 2016, and December 31, 2021 and were examined retrospectively. In 54.2% of the patients (n=141), three or more minor dysmorphic features were observed, and structural anomalies were present in 32.3% of patients. Accompanying global developmental delay was found in 55.4% (n=144) of patients, and epilepsy was detected in 16.9% (n=44). The most common cranial MRI findings were abnormal signal intensities, ventricular enlargement and asymmetry, and corpus callosum anomalies. The presence of structural anomalies and accompanying global developmental delay was significantly higher in patients with three or more minor dysmorphic features. Genetic diagnosis consistent with the clinical phenotype was present in 51 patients (%19,6). It was observed that no genetic etiology could be established in 209 (80.4%) patients although at least one genetic test was performed. In patients with a genetic diagnosis, copy number variations were represented in 39.2% (n=20), single gene disorders in 35.29% (n=18), trinucleotide repeat disorders in 17.6% (n=9), and chromosomal disorders in 7.8% (n=4) of patients. The presence of global developmental delay, epilepsy, structural anomalies, and three or more minor dysmorphic features was significantly higher in patients with a genetic diagnosis compared to that of the patients without a genetic diagnosis.