The behavioral phenotype in a cohort of patients with chromosome 18 anomalies: a retrospective observational study.

Background: Genetic syndromes resulting from chromosome 18 structural abnormalities constitute a broad spectrum of conditions characterized by significant clinical heterogeneity. Most studies in the literature focus on case reports and clinical observations; the present study aims to assess the cognitive, communicative, behavioral, and adaptive abilities of different chromosome 18 abnormalities. In addition, this work aims to identify phenotype-genotype correlations by comparing individuals with 18p deletion, 18q deletion, and 18p tetrasomy.

Methods: The sample included 24 patients with a definite genetic diagnosis of 18p deletion (N = 6), 18q deletion (N = 9), or 18p tetrasomy (N = 8). The assessment is provided by using a specific protocol based on direct and indirect clinical assessment of patients. Differences in IQ/GQ indexes, adaptive behavior, CARS scores, and CBCL internalizing and externalizing symptoms were assessed using ANCOVAs with age as covariate.

Results: Our results showed more significant cognitive and behavioral impairment in tetrasomy 18 than in the other two conditions. Conversely, in 18p deletion group, we found greater behaviorally susceptibility to develop autistic traits.

Conclusion: These preliminary findings should raise clinicians' awareness of the strengths and weaknesses of patients with chromosome 18 alterations, paving the way to targeted and more appropriate management.