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.