Supplementary Material for: Prenatally Diagnosed De Novo Interstitial Duplication in 2p21p24.3 with Unique Manifestations: Case Report

Introduction
Partial duplications involving chromosome 2p are rare genomic events associated with variable phenotypic outcomes, ranging from craniofacial abnormalities, organ malformations to developmental delays. Prenatal identification of such duplications has become increasingly common with advances in chromosomal microarray technology, but predicting postnatal manifestations remains challenging. This report presents a de novo 32 Mb duplication of 2p21p24.3, detected prenatally, in a male infant who demonstrated unique clinical features and multisystem involvement postnatally.
Case Presentation
A 29-year-old pregnant female was referred for genetic evaluation following prenatal detection of flat nasal bridge, frontal bossing, short extremities, small penis and suspected hypospadias. Chromosomal microarray analysis revealed a 32 Mb duplication of 2p21p24.3, confirmed as de novo by parental testing. Postnatally novel features such as subglottic hemangioma, preauricular pit, and behavioral symptoms related to facial contact were noted. Growth delay, craniofacial dysmorphism, congenital heart defects, and genital anomalies were also observed.
A multidisciplinary approach involving clinical genetics was critical for addressing the patient’s complex medical needs. Despite ongoing supportive care, the patient continues facing significant developmental and medical challenges, underscoring the need for long-term follow-up as well as genotype-phenotype correlations.
Conclusion
This case broadens the clinical spectrum of partial trisomy 2p by documenting unique features, including subglottic hemangioma, behavioral symptoms and preauricular pit. It highlights the value of integrating prenatal diagnostics with detailed postnatal phenotypic assessment to improve understanding of genotype-phenotype correlations in rare chromosomal duplications. Although the PPP1CB gene within the region is might considered a plausible candidate for explaining the some of the patient’s cardinal features, dysmorphism(prominent forehead, preauricular ear pits, low-set, posteriorly rotated ears), cardiac-neurological problems, other genes associated with defined syndromes—whose clinical manifestations overlap to varying degrees—were also considered as potential contributors to the clinical picture, such as MYCN, DNMT3A, DPYSL5, and SOS1. These insights can aid clinicians in genetic counseling, anticipatory guidance, and management of similar cases in the future.