Short report: Twins with 20p13 duplication. Case report and comprehensive literature review

• Published in: Molecular genetics & genomic medicine 2024-05, Vol.12 (5), p.e2436-n/a
• Main Authors: Kennedy, Benjamin J., Savage, Sarah K., Kaler, Stephen G.
• Format: Article
• Language: English
• Subjects: 20p13 duplication; Asthma; Autism; Axonal transport; Axons; Birth weight; Child, Preschool; Chromosome 20; Chromosome aberrations; Chromosome Duplication; Chromosomes; Clinical Report; Clinical Reports; Cognition; DNA microarrays; gene duplication; Genetic screening; Humans; Literature reviews; Male; Males; Morphogenesis; Nose; Organoids; Phenotypes; Polymorphism, Single Nucleotide; Single-nucleotide polymorphism; syntaphilin; Trisomy; Trisomy - genetics; trisomy 20p; Twins; Twins, Monozygotic - genetics; twin‐twin transfusion syndrome
• ISSN: 2324-9269; 2324-9269
• DOI: 10.1002/mgg3.2436

Background Trisomy 20p is a rare genetic condition caused by a duplication of the short arm of chromosome 20. Methods We employed clinical observation and molecular genetic testing (SNP microarray), to study identical twin males with an unknown dysmorphic syndrome. We conducted a literature review of trisomy 20p and collated the clinical and molecular genetic findings on 20 affected subjects reported since 2000. Results Identical twin males, whose prenatal course was complicated by a twin‐to‐twin transfusion, manifested profound language and neurocognitive delays as well as distinctive facial dysmorphisms when evaluated at 2 years of age. SNP microarray identified identical duplications of 20p13 with no other chromosomal aberrations. A literature survey of 20p trisomy syndrome identified 20 other examples of this condition reported since 2000, which we collated with 33 summarized by Sidwell et al. (2000). Within the combined total of 55 affected individuals, we found a distinctive clinical phenotype that provides insight on the effects of abnormal dosage of genes in 20p13. These loci include FAM110A (OMIM 611393), ANGPT4 (OMIM 603705), RSPO4 (OMIM 610573), PSMF1 (OMIM 617858), SNPH (OMIM 604942), SDCBP2 (OMIM 617358), FKBP1A (OMIM 186945), TMEM74B, C20orf202, and RAD21L1 (OMIM 619533). Gene profiling highlighted that syntaphilin (SNPH) is highly expressed in mammalian brain, where it is considered critical for mitochondrial transport in neuronal axons, and to directly influence axonal morphogenesis and function. Conclusion We propose that abnormal activity of syntaphilin engendered by the trisomy is primarily responsible for the language, neurocognitive, and gross motor delays reported in individuals with 20p trisomy. Additional studies, for example, characterization of cerebral organoids generated from affected patients may help to better understand this condition, and potentially suggest rational remedies to improve the lives of affected individuals and their families. (a) Facial dysmorphism in twins with 20p13 duplication. Note thin hair, deep‐set eyes, hypertelorism, narrow palpebral fissures, long eyelashes, broad nasal bridge; bulbous nose, and long philtrum. Age: 2 years, 2 months. (b) T1‐weighted midline sagittal image in Twin 1. Mild nonspecific prominence of supratentorial sulci and cisterns consistent with mild cerebral volume loss (arrows). Minimal increased FLAIR signal consistent with periventricular gliosis or leukomalacia. (c) Dysmorphic fa