Double Aneuploidy (Trisomy 21 and XXX) in a Child with Down Syndrome Phenotype: A Case Report with Review of Literature

Abstract

Abstract Background: Down syndrome is the most common and extensively studied disorder arising out of human chromosomal aberration. Several aneuploidies are associated with Down syndrome, but double trisomy (48 XXX + 21) is rarely described. Clinical Description: A 3-year-old girl presented with respiratory distress and a chronic history of feeding fatigue and failure to thrive. She had phenotypic features suggestive of Down syndrome and clinical signs of acyanotic heart disease in congestive cardiac failure. Management and Outcome: Echocardiography revealed ventricular septal defect and atrial septal defect. Karyotyping showed double trisomy (trisomy 21 and XXX). Trisomy X was an incidental finding on karyotyping with no clinical features suggestive of XXX syndrome specifically at this age. The patient was managed conservatively with decongestive therapy for congestive heart failure and oral sildenafil for pulmonary hypertension. Additional evaluations were done to identify associated anomalies, and the parents were counseled. Conclusion: Down and XXX syndromes share many clinical signs and symptoms, making karyotyping the only way to make an early diagnosis. A child having a phenotype characteristic of Down syndrome may have an unsuspected double trisomy of X chromosome along with 21 trisomy, which can only be identified by karyotyping.