Rare Double Aneuploidy (Down-Klinefelter Syndrome): A Case Report

Abstract

Double aneuploidies, such as Down syndrome and sex chromosome aneuploidies, are relatively rare. One rare form of double aneuploidy, Down-Klinefelter syndrome, is described here. The phenotypic characteristics of a three-year-old child showed the presence of features typical of Down syndrome. He had a global developmental delay, small testes, and diabetes mellitus by 18 months of age. Regardless of the presenting clinical features, karyotyping should be performed in all patients with suspected Down syndrome. In Down-Klinefelter syndrome, anticipatory phenotype goes beyond the sum of individual syndromic characteristics.

Keywords: 48xxy+21; diabetes mellitus; double aneuploidy; down's syndrome; down-klinefelter syndrome; klinefelter's syndrome.

Figure 1. Complete karyotype of the child with Down-Klinefelter syndrome from peripheral blood lymphocytes revealed 48,XXY,+21

Figure 2. A FISH analysis showed three copies of sex chromosome (two copies of X chromosome and one copy of Y chromosome), and three copies of chromosome 21

FISH - fluorescence in situ hybridization

Figure 3. Frontal photograph of a three-year-old boy with Down-Klinefelter syndrome showing typical facial features of Down syndrome; flattened nose, upward slanting eyes, small ears, small mouth, and protruded tongue

Figure 4. Lateral photograph of the patient with Down-Klinefelter syndrome showing low set and small ear, flat occiput, and protruded tongue

Figure 5. Photograph of the left hand of the patient with Down-Klinefelter syndrome showing transverse palmar crease (simian crease): a single line that runs across the palm of the hand