Clinical characterization of a child with de novo partial trisomy 9p24-9q12
Background: Partial trisomy 9p is considered the fourth most frequently reported trisomy in live births, following trisomies 21, 18, and 13. This relatively high incidence is observed, probably, due to the limited number of genes involved within the 9p24-9q12 region. With a frequency of less than 1 in 1,000,000 live births, it is classified as a rare disease. The aim of the study:To describe the phenotypic characteristics of a child with de novo partial trisomy 9p and compare them with previously documented cases in the international literature. Materials and methods: A descriptive case report of a 4-year-old male patient with global neurodevelopmental delay and dysmorphic features evaluated at the William Soler University Pediatric Hospital. Clinical, anthropometric, dermatoglyphic, imaging (computed tomography, echocardiography, ultrasound), and audiometric (brainstem auditory evoked potentials) assessments were carried out. Cytogenetic analysis was performed on peripheral blood lymphocyte cultures using the synchronization method, with high-resolution GTG-banded karyotyping. Fluorescence in situ hybridization (FISH) was used to characterize the supernumerary chromosome with VYSIS (Abbott) probes. The clinical and cytogenetic findings were compared with previously published cases. Results: A 4-year-old male patient presented with global neurodevelopmental delay and distinctive facial dysmorphisms. At birth, he exhibited cyanosis and an absence of the crying and sucking reflexes. He was subsequently noted to have severe neurodevelopmental delay from the first month of life, and initially presented with hypotonia, which improved following physical therapy. His social development was poor, and language development was nearly non-existent. Physical examination revealed low height and weight for his age, alongside multiple facial dysmorphic features. He was also diagnosed with a Dandy-Walker malformation, pulmonary valve dysplasia, and an 8 mm atrial septal defect. Karyotyping identified a large supernumerary chromosome, which, via GTG banding, was characterized as partial trisomy 9p, consistent with the chromosomal formula: 47,XY,+del(9)(q12q34.3). Cytogenetic analysis of both parents showed a normal constitution. Conclusion: The patient's clinical findings were consistent with those reported in the literature, which, in conjunction with conventional cytogenetic studies, led to the diagnosis of de novo partial trisomy 9p
García-García A, Galarza JE, Castelvi A, et al. Clinical characterization of a child with de novo partial trisomy 9p24-9q12. Research Results in Biomedicine. 2026;12(2):175-182.
DOI: 10.18413/2658-6533-2026-12-2-0-1
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