Background: The incidence of sex chromosome aneuploidies is 1:400. Klinefelter syndrome is considered to be the most common type of sex chromosome aneuploidy, manifested as variants, such as 48,XXXY, 48,XXYY and 49,XXXXY. Nondisjunction of the X chromosome during meiosis I and II is considered as the cause of this type of aneuploidy. The classic clinical presentation of Klinefelter Syndrome is a triad of hypogonadism, mental retardation, and musculoskeletal anomalies.
Case Presentation: In this case report, we describe a 2-year-old male child identified postnatally to have low birth weight, congenital heart defect, inguinal hernia, facial dysmorphism, and genital organs anomalies. Chromosomal analysis revealed a karyotype of 49,XXXXY and the comparative genomic hybridization (CGH) array analysis revealed a 155,065 kilo base pair duplication on chromosome Xp22.33q28 (168,546, −155,233,731) X4.
Conclusion: 49,XXXXY karyotype is considered as the rarest sex chromosome aneuploidy syndrome. To our knowledge, this study is the first report of a patient with 49,XXXXY syndrome from Oman.
Key words: Aneuploidy, dysmorphism, 49, XXXXY, Klinefelter syndrome
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