Symmetrical bronchial pattern with normal atrial morphology.

An infant with trisomy 21 and tracheostenosis is described. Postmortem findings included symmetrical bronchi, normal atrial arrangement ("situs") and anomalous thoracic vessels. The lack of concordance between the bronchial morphology and atrial arrangement supports the premise that atrial morphology is a more accurate predictor of the presence or absence of the isomerism syndromes.