Case Study

Down syndrome

by Laura L. Williams, M.D.
Instructor of Pediatrics–Neonatology

This 2800-gram, appropriate-for-gestational-age female was born at term to a 32-year-old primigravida mother. The pregnancy was complicated by polyhydramnios. Maternal laboratory values were normal except for a positive group B streptococcal culture. The mother declined a triple screen. During labor, the mother received two doses of clindamycin. Spontaneous rupture of the fetal membranes occurred 8.5 hours before delivery. The Apgar scores were 7 at 1 minute, 8 at 5 minutes. After delivery, 40 mL of nonbilious fluid was suctioned from the newborn’s stomach.

The infant was transferred to the level 2 nursery for mild respiratory distress. Oxygen saturations were recorded in the mid to high 80s on room air and corrected with oxygen by hood. Examination suggested trisomy 21 (Down syndrome), but was otherwise unremarkable. An abdominal radiograph was significant for the presence of a double bubble; a chest radiograph was interpreted as normal.

The infant was transferred to Texas Children’s Hospital and was quickly weaned to room air. Echocardiogram showed left aortic arch, complete common AV canal, ostium primium ASD, a moderate patent ductus arteriosis, mild right ventricular dilation, and moderate right and left atrium dilation. Patient remained hemodynamically stable throughout the hospitalization. A UGI examination demonstrated a high-grade duodenal stenosis with malrotation, which was repaired with duodenoduodenostomy; a Ladd procedure and appendectomy also were performed. Initial nutritional support was provided by total parenteral nutrition (TPN) and lipids. The infant was later advanced to expressed breast milk (EBM). Thyroid studies were normal. A chromosome analysis was consistent with trisomy 21.

Discussion: Trisomy 21 is a common chromosomal anomaly. Infants with this condition have characteristic facies (microcephaly, brachycephaly, flat facial profile secondary to midface hypoplasia, flat nasal bridge, upwardly slanted palpebral fissures, epicanthal folds, protruding tongue), excess posterior nuchal skin, clinodactyly of fifth digit, unilateral or bilateral single palmar creases, broad hands, and hypotonia. The incidence of celiac disease, intestinal atresia (esophageal, duodenal atresia, ileal, and anal), Hirschsprung disease, and cardiac anomalies (endocardial cushion defects, ventricular septal defect) all are increased. The incidence of trisomy 21 is 1 in 800 live births; 94% is due to trisomy 21, the remainder is secondary to translocation or mosaicism.

Prenatal diagnostic screening is done most often by a triple screen test, which has 60% sensitivity and 90–95% specificity. Positive screens should be investigated by fetal chromosomal analysis. A second-trimester ultrasound also may be helpful. Postnatal diagnosis is suggested by characteristic facies or the presence of classically associated medical conditions. Karyotyping remains the definitive diagnostic test.

Management is dictated initially by the immediate medical or surgical needs and normal newborn care. Later medical issues include short stature, obesity, mental retardation, alanto-axial instability, hypothyroidism, diabetes mellitus, and leukemia. Therefore, patients with trisomy 21 require a multidisciplinary approach throughout life.