Beyond the Syndrome: Extensive Congenital Abnormalities in an Infant With Trisomy 21

Area of Science:

• Pediatric Cardiology
• Medical Genetics
• Congenital Abnormalities

Background:

• A female infant with trisomy 21 presented with a complex congenital heart defect: Rastelli Type C complete atrioventricular septal defect (AVSD), tetralogy of Fallot, and a right aortic arch.
• The infant underwent a palliative modified Blalock-Taussig-Thomas shunt (mBTTS) due to hypoxemia from progressive right ventricular outflow tract obstruction.

Observation:

• Autopsy revealed multiple rare concomitant findings, including abdominal adhesions with transverse colon stenosis, elongated intestinal villi, a small bowel polyp, and an anomalous tracheal bronchus.
• The infant exhibited severe pulmonary hypertensive arteriolar changes disproportionate to her condition and refractory anasarca with recurrent chylous pleural effusions, potentially indicative of systemic capillary leak syndrome (SCLS).

Findings:

• The constellation of cardiac, gastrointestinal, airway, and vascular anomalies in this trisomy 21 case is highly unusual and not previously described.
• Severe pulmonary hypertension and systemic capillary leak syndrome were significant complications impacting the infant's clinical course.

Implications:

• This case highlights the potential for extreme phenotypic variability in trisomy 21, presenting a unique combination of rare congenital abnormalities.
• Understanding such extreme phenotypes is crucial for accurate diagnosis, management, and genetic counseling in complex pediatric cases.