Abstract
BackgroundSubtelomeric deletions of the long arm of chromosome 20 are rare, with only 11 described in the literature. Clinical features of individuals with these microdeletions include severe limb malformations, skeletal abnormalities, growth retardation, developmental and speech delay, mental retardation, seizures and mild, non-specific dysmorphic features.Methodology/Principal FindingsWe characterized microdeletions at 20q13.33 in six individuals referred for genetic evaluation of developmental delay, mental retardation, and/or congenital anomalies. A comparison to previously reported cases of 20q13.33 microdeletion shows phenotypic overlap, with clinical features that include mental retardation, developmental delay, speech and language deficits, seizures, and behavior problems such as autistic spectrum disorder. There does not appear to be a clinically recognizable constellation of dysmorphic features among individuals with subtelomeric 20q microdeletions.Conclusions/SignificanceBased on genotype-phenotype correlation among individuals in this and previous studies, we discuss several possible candidate genes for specific clinical features, including ARFGAP1, CHRNA4 and KCNQ2 and neurodevelopmental deficits. Deletion of this region may play an important role in cognitive development.
Highlights
Because molecular cytogenetic techniques such as microarraybased comparative genomic hybridization can identify chromosome abnormalities in individuals with nonspecific symptoms, such as developmental delay, without the need for clinical suspicion of a specific disorder, these techniques have enabled a ‘‘genotype-first’’ approach to the genotype-phenotype characterization of rare chromosome abnormalities
High-resolution microarray analysis can detect small DNA imbalances that may reveal the causative genes for specific clinical features, which can can aid diagnosis and prognosis
Subtelomeric deletions of the long arm of chromosome 20 are rare, with only 11 described in the literature [2,3,4,5,6,7,8,9,10,11]. Of these previously reported subtelomeric deletions, five individuals have been well characterized by microarray analysis [7,8,9,11]
Summary
Because molecular cytogenetic techniques such as microarraybased comparative genomic hybridization (aCGH) can identify chromosome abnormalities in individuals with nonspecific symptoms, such as developmental delay, without the need for clinical suspicion of a specific disorder, these techniques have enabled a ‘‘genotype-first’’ approach to the genotype-phenotype characterization of rare chromosome abnormalities. Clinical features of individuals with these microdeletions include severe limb malformations, skeletal abnormalities, growth retardation, developmental and speech delay, mental retardation, and seizures. Clinical features of individuals with these microdeletions include severe limb malformations, skeletal abnormalities, growth retardation, developmental and speech delay, mental retardation, seizures and mild, non-specific dysmorphic features
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