Diagnostic confusion of COVID-19 versus plastic bronchitis in a patient with trisomy 21: A case report

Introduction

Plastic bronchitis (PB) is a rare but potentially life-threatening pulmonary disorder characterized by the formation of cohesive bronchial casts capable of obstructing airways and causing severe respiratory distress. Although it is more frequently associated with pediatric populations, particularly those with congenital heart disease, PB has been increasingly recognized in adults, often with diverse and underrecognized etiologies. Distinguishing between inflammatory (Type I) and lymphatic (Type II) cast subtypes is critical for guiding diagnosis and management. This report describes a rare case of adult-onset PB in a patient with trisomy 21, an association not previously well-documented.

Case presentation

A 30-year-old female with trisomy 21 presented with acute hypoxemia, perioral cyanosis and productive cough with expectoration of whitish bronchial casts. She had a prior history of COVID-19 pneumonia but no congenital heart disease or recurrent infections. Initial chest imaging revealed mosaic perfusion and pericardial effusion, and bronchoscopy identified whitish filamentous material partially obstructing the bronchi. Histopathological examination of the casts revealed fibrin bands with inflammatory cells, consistent with Type I inflammatory PB. The patient responded initially to corticosteroid therapy; however, symptoms recurred upon withdrawal, necessitating repeated steroid courses. Bronchoscopic removal of casts led to symptomatic improvement. No alternative infectious or structural causes were identified.

Conclusion

This case highlights the need to consider plastic bronchitis in the differential diagnosis of adults presenting with acute hypoxemic respiratory failure, particularly when clinical and imaging findings mimic COVID-19 pneumonia. It underscores the importance of combining imaging, bronchoscopy, and histopathology for diagnosis, and the therapeutic role of corticosteroids in managing inflammatory PB. To our knowledge, this is one of the first reported cases of PB in an adult with trisomy 21, expanding awareness of its occurrence beyond traditional pediatric and congenital heart disease contexts.