Chromosome 1q21.1 duplication syndrome, also known as 1q21.1 microduplication, is an uncommon condition first reported by Mefford et al. (2008). The syndrome is estimated to occur in 1 out of 6309 live births and to have a prevalence of 0.03% in adults (Huang et al. 2023). The common phenotypic features in 1q21.1 microduplication include developmental delay, macrocephaly, autism or autistic behaviors, and mild to moderate mental retardation. Schizophrenia and related psychotic disorders seem to be associated with loci at the q21.1 location. In addition, cardiovascular disorders, particularly tetralogy of Fallot, might be evident along with neurological manifestations (Dolcetti et al. 2013). In terms of dysmorphism, some patients may have slight hypertelorism, bitemporal narrowing, broad nasal bridge, syndactyly, etc. However, some affected individuals, despite having duplication at the 1.q21.1 location, do not display any identified behavioral, developmental, or physical anomalies. Other less common features related to the syndrome are provided in detail in Table 1.