# Severe Early-Onset Pulmonary Hypertension in a Six-Month-Old With Down Syndrome and Isolated Secundum Atrial Septal Defect

## TL;DR

A six-month-old with Down syndrome developed severe pulmonary hypertension from a small heart defect, requiring urgent treatment and highlighting the need for early intervention in such cases.

## Contribution

Highlights the atypical progression of secundum ASD to severe PAH in infants with Down syndrome and the effectiveness of early pulmonary vasodilator therapy.

## Key findings

- Infant with Down syndrome developed severe PAH from a rapidly enlarging secundum ASD.
- Early treatment with sildenafil and oxygen stabilized the infant within five days.
- Emphasizes the importance of early cardiac evaluation and multidisciplinary care in Down syndrome infants with heart defects.

## Abstract

Infants with Down syndrome (trisomy 21) commonly present with congenital heart defects and immune dysregulation, significantly increasing the risk of early-onset pulmonary arterial hypertension (PAH). Although secundum atrial septal defects (ASDs) are often considered hemodynamically mild in non-syndromic children, they can progress aggressively in the presence of trisomy 21. We describe a six-month-old male infant with karyotype-confirmed trisomy 21 who developed severe PAH secondary to a rapidly enlarging secundum ASD - a highly atypical presentation for an isolated lesion. The infant presented with fever, respiratory distress, vomiting, and diarrhea, alongside a clinical history of neonatal sepsis, recurrent infections, failure to thrive (weight below the 5th percentile), and subclinical hypothyroidism (TSH 8.12 μIU/mL). Echocardiography revealed that the ASD had enlarged from 6 mm at five months to 10 mm, creating a substantial left-to-right shunt (Qp:Qs >1.5:1). Management with IV ceftriaxone, sildenafil (2 mg twice daily), supplemental oxygen, and nutritional support stabilized the infant within five days (SpO₂ 93-94% on room air). He was discharged for deferred surgical ASD closure, highlighting the value of early pulmonary vasodilator therapy as a bridge to definitive repair. This case underscores the markedly increased susceptibility of infants with Down syndrome to severe PAH, even in the setting of a seemingly hemodynamically insignificant ASD. Early cardiac evaluation, prompt intervention, and multidisciplinary management are crucial to preventing irreversible pulmonary vascular disease in this high-risk population.