Histopathologic Features of Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins with Atypical Clinical Presentation.

Abstract Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare neonatal lung disease with fatal outcome. Typically, respiratory symptoms present in the first 24 hours of life and patients die within the neonatal period. Atypical, delayed clinical presentations and/or longer survival have also been reported. Here, we studied the clinicopathologic relationship of ACD/MPV by examining 16 cases of ACD/MPV, focusing on atypical features. Based on the presence of diffuse vs. focal/patchy ACD/MPV histopathologic changes, we divided the cases into classic and non-classic pathology groups. MPV was found in all ACD/MPV. Ten of sixteen cases exhibited classic diffuse abnormalities, while six of sixteen had a non-classic focal/patchy distribution. However, among seven patients with atypical clinical features, only two had non-classic pathology, while four out of nine clinically typical cases had non-classic ACD/MPV pathology. Marked intrapulmonary aberrant arteriovenous vessels were present in all atypical cases. In conclusion, clinical presentation is not always correlated with histopathology in ACD/MPV. Atypical ACD/MPV should be suspected in any infants with fulminant pulmonary hypertension. Abnormal pulmonary veins and aberrant intraseptal vessels are the most important clues for diagnosis. Additional studies are needed for further elucidation of diagnostic histological criteria of atypical ACD/MPV and to explore its pathogenesis.