Mosaic double aneuploidy: Down syndrome and XYY
Patient was a 17-month-old boy with growth retardation and developmental delay, the third child of non-consanguineous parents. The father was 37-year-old and the mother was 31-year-old at conception. The antenatal period was uneventful. The child weighed 2.2 kg at birth. The two older siblings were normal and there was no significant family history.\nClinical examination revealed an interactive and social child. His height at admission was 76 cm and weight, 8.65 kg, which were within the normal limits for Down syndrome charts. The phenotype was consistent with Down syndrome with flat facies, hypertelorism, mongoloid slant of the eyes, epicanthal folds and flat nasal bridge, low-set posteriorly placed ears, small abnormal pinnae, short neck and increased sandal gap. Vision and hearing screening tests were normal. He had hypotonia with exaggerated deep tendon reflexes, hyperextensible elbows, knees and fingers and a flexible calcaneovalgus deformity. He was able to sit with support, grasp objects, recognize parents and vocalize. Neurodevelopmental assessment revealed a developmental age of 7 months. There were no other significant physical findings. Blood investigations including thyroid screening were normal.\nConventional cytogenetic analysis of phytohemagglutinin-stimulated peripheral blood showed trisomy 21 in all 25 metaphases. Six metaphases showed double aneuploidy with an associated XYY [], which was confirmed by fluorescence in situ hybridization (FISH) analysis [] using the centromeric probes for chromosomes X and Y (Abott Molecular, Abbott Park, IL, USA). The karyotype of the child was 47, XY,+21[19]/48, XYY,+21[6]; in situ hybridization XYY (DXZ1 × 1, DYZ1 × 2). Parental karyotypes were not available.