Aplasia/Hypoplasia of the lungs Acinar dysplasia 2020-10-12T11:21:18Z Arrest of lung development in the pseudoglandular stage (weeks 8 to 16 of human gestation) resulting in small sized lungs, predominantly composed of bronchial and bronchiolar structures embedded in abundant loose mesenchyme that is poorly vascularized. Acinar structures are essentially absent, with no significant formation of saccules and no alveoli.