Children born with chromosome 15 syndromes often experience marked developmental delays. However, notable heterogeneity exists across children, which may reflect a combination of their specific genetic mutation and environmental or epigenetic factors. Within the present case report, we detail the developmental trajectories of two exceptional half-brothers with chromosome 15 syndromes and elevated genetic risk for autism spectrum disorder (ASD). One child’s genetic mutation is consistent with Chromosome 15q11.2–13.1 duplication syndrome (Dup15q), while his brother has mosaicisms for both Dup15q and a deletion on chromosome 15 (del 15q11.2q13), often referred to as Angelman syndrome (AS). Ultimately, well over half of children with Dup15q duplications also receive an ASD diagnosis (~ 69–92%; Betancur & Coleman,
2013; Wegiel et al.,
2012). However, ASD-specific concerns/expression in Dup15q also present differently as a function of the inherited duplication (e.g., maternally derived-phenotypical ASD present; paternally derived-phenotypical ASD absent; as reviewed in Betancur & Coleman,
2013). Similar to children with Dup15q, roughly 63% percent of children with AS also receive an ASD diagnosis (50–81%; Betancur & Coleman,
2013). In a majority of cases, AS is derived from a deletion of the mother’s genetic contribution from the 11.2 to 13.1 region of chromosome 15 that contains the protein ubiquitin protein ligase E3A (UBE3A; Chamberlain & Lalande,
2010; Williams et al.,
2010). However, AS may also result from imprinting defects, mutations in the maternal copy of UBE3A, and inheritance of two paternal chromosomes and no maternal copies of chromosome 15 (Bird,
2014; Chamberlain & Lalande,
2010; Dagli et al.,
2011; Margolis et al.,
2015; Tan et al.,
2011; Williams et al.,
2010). This study provides a unique opportunity to better understand at what age and through what measures ASD symptoms may be detected and potentially reach a diagnostic (i.e., clinically significant) threshold for children with these syndromes, while also providing insight on the measurement of developmental competencies in these syndromes. Therefore, the aims of this case series are three-fold and include documenting and understanding the following across Dup15q and AS: (1) detailed profiles of developmental progress across the first 5 years of life, (2) social development and autism emergence, and (3) measurement fit for syndromic development. …
