Rationale: Copy number variants (CNVs) are structural genomic alterations that can lead to a range of genetic disorders by disrupting gene dosage and function. Large duplications affecting multiple genes are known to result in partial trisomies, frequently associated with developmental delay, intellectual disability, and congenital anomalies. These types of CNVs often arise from unbalanced chromosomal translocations, typically inherited from phenotypically normal carriers of balanced rearrangements. This study describes the clinical and cytogenomic findings of a rare case of a dysmorphic infant with concurrent partial trisomies of chromosomes 9p and 12p. Patient concerns: A female infant presenting with global developmental delay, growth retardation, distinctive craniofacial dysmorphism, and multiple congenital anomalies. Conventional karyotype, along with genome sequencing-based CNV analysis, has been performed. In addition, parental karyotyping has been performed. Diagnoses: The infant’s karyotype revealed an extra copy of a structurally abnormal chromosome 9. Genome sequencing-based CNV analysis identified 2 pathogenic CNVs: a duplication of chromosome 9p24.3-q21.13 and a second duplication of chromosome 12p13.33-p12.1, indicating 2 partial trisomies of chromosome 9p and 12p. Parental karyotyping revealed a maternally inherited balanced translocation involving chromosomes 9 and 12. Interventions and outcomes: The patient received supportive care; at 12 months of age, she developed a severe respiratory infection and died. Lessons: This case contributes to the expanding phenotypic and cytogenomic spectrum of partial trisomies 9p and 12p. We highlight the role of CNV analysis based on genome sequencing in the clinical evaluation of individuals with dysmorphic and malformative conditions. We also emphasize the importance of parental cytogenetic studies in such cases for elucidating inheritance patterns and recurrence risks.
Azher et al. (Fri,) studied this question.
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