What should we consider in the case of combined Down- and 47,XY,+i(X)(q10) Klinefelter syndromes? The unique case of a male newborn and review of the literature

Down-Klinefelter Syndrome With Concurrent Double Aneuploidy in an Indian Child

The genetics of Down syndrome (DS) and Klinefelter syndrome (KS) are a nondisjunction of autosomal and sex chromosomes, respectively, resulting in aneuploidies. Less than 70 cases of concurrent Down-Klinefelter syndrome (DS-KS) have been reported in the literature. We report the case of a five-month-old Indian child with a rare double aneuploidy resulting in DS-KS. A five-month-old boy born to non-consanguineously married parents presented with failure to thrive and dysmorphic facies. The family history was unremarkable. On examination, he had an upward eye slant, a depressed nasal bridge, a horizontal crease in the left hand, and a sandal gap. A clinical diagnosis of the Down phenotype was considered. Karyotype analysis revealed the presence of double aneuploidy (48, XXY,+21) suggestive of DS-KS. Down-Klinefelter syndrome presents with the DS phenotype at birth, and the characteristic KS phenotype develops in early infancy and apparently manifests during puberty only. Early diagnosis is required for parental counseling and planning for future pregnancies. In children with a typical Down syndrome phenotype, chromosomal analysis is highly recommended. The diagnosis of DS-KS at the earliest has implications for these children's short-term and long-term outcomes. It helps in planning the subsequent pregnancy with appropriate genetic testing and counseling to avoid the risk of another child with trisomy.

Down-Klinefelter Syndrome (48,XXY,+21) in a Saudi Neonate: A Case Report and Literature Review

Aneuploidy is a category of chromosomal abnormalities involving a numerical abnormality of the chromosomes. The most common type seen in live-born babies is trisomy. Double aneuploidy that leads to trisomy of two different chromosomes occurs due to accidental meiotic nondisjunction events; both can have the same or a different parental origin. Other frequently found double aneuploidies include 48,XXX,+21; 48,XXY,+18, and 48,XXX,+18. Here, we report the case of double aneuploidy (Down-Klinefelter syndrome) in a Saudi newborn with the clinical features of Down syndrome, along with hypothyroidism and congenital heart disease, who was admitted to our neonatal intensive care unit. To our knowledge, this is the first case of its kind reported from the Kingdom of Saudi Arabia.

CHROMOSOMAL DISEASES IN THE HUMAN PATHOLOGY

Background. Chromosomal diseases are the cause of 45-50 % of multiple birth defects. Basic research on mutations is performed using genomic technologies to identify a correlation between genotype and phenotype in aneuploidies and to understand its pathogenesis. Objective. The aim of the research is to study the etiology, pathogenesis of symptoms and diagnostics for patients with Down, Klinefelter, Turner syndromes and double aneuploidies by 21 and sex chromosomes. Methods. A literature review by the keywords “Down syndrome”, “Klinefelter syndrome”, “Turner syndrome”, “double aneuploidy” for the period of 2000-2020 was carried out. Results. Down, Klinefelter and Turner syndromes are the most common aneuploidy among viable newborns. Frequency of meiotic non-disjunction events causing these aneuploidies increases with the age of a woman. Identified genes are responsible for pathogenesis of symptoms in trisomy 21, Turner and Klinefelter syndromes. Diagnostics of chromosomal diseases includes prenatal screening programs and postnatal testing. Conclusions. Cytogenetic variants of Down syndrome are simple complete trisomy 21, translocation form and mosaicism. Trisomy 21 is associated with advanced maternal age. Phenotypic manifestations of Down syndrome are associated with the locus 21q22. The maternal and parental nondisjunction of X-chromosomes in meiosis causes Klinefelter and Turner syndromes. These chromosomal diseases are variants of intersexualism with intermediate chromosomal sex. Down-Klinefelter and Down-Turner syndromes are double aneuploidies. Patients have a Down syndrome phenotype at birth, and signs of Klinefelter and Turner syndromes occur during puberty. Diagnosis of aneuploidy is based on the cytogenetic investigation (karyotyping), DNA analysis, ultrasonography and biochemical markers of chromosomal pathology.