Acinar Dysplasia, Clinical and Pathological Diagnosis Dilemma in Term Infants

Introduction: Progressive respiratory distress in infants represents a diagnosis challenge for a neonatologist. Acinar dysplasia is a fatal congenital disease. This form of primary pulmonary hypoplasia should be differentiated from other causes of respiratory failure in infants such as Surfactant Protein B Deficiency or type 3 Cystic Adenomatoid Malformation

Case report: A male infant was born at term to an 18 years old primigravida. Antenatal follow-up was insignificant. The parents are healthy and cousins. The infant was born vaginally with Apgar Score of 8 and 9. Birth weight was 3195 gm. few hours after birth, the infant developed progressively severe respiratory distress, which required intubation and mechanical ventilation. The chest x-ray showed evidence of severe respiratory distress syndrome Figure (1). Gradually, the respiratory status worsened that requires high frequency ventilator and 3 doses of natural surfactant, producing only a minimal transient response. The infant received a short course of steroid then trial of nitric oxide for 5 days, but he did not improve. Echocardiogram done and it was normal. All cultures result were negative. Sequence analysis of the genomic DNA, does not confirm the diagnosis of surfactant Protein SP-B deficiency. Open lung biopsy was done on the 3rd week of life and it was consistent with acinar dysplasia Figure (2). On the 22nd day of life the infant develop significant bilateral pneumothorax and chest tube were inserted. Shortly thereafter, at the age of 28 days, the infant expired.

Discussion: Lung development occurs by a process of branching morphogenesis combined with epithelial differentiation. Absence of alveolar development, with airway distal to bronchi composed of irregularly branching bronchiolar structure lined by ciliated epithelium. This malformation, formed acinar dysplasia. Microscopically AD resemble type 3 CAM except that cartilage is absent in the later.1, 2. Their macroscopic appearances differs. A CAM is large and compresses adjacent structures, including unaffected lungs, while AD causes hypoplasia of all lung tissue. AD causes pulmonary hypoplasia due to total failure of development distal to terminal bronchioles without hyperplasia. Infant with Surfactant Protein B Deficiency (SP-B Deficiency) the lamellar bodies are absent. The presence of dysplastic lung tissue on histo-pathology and lamillar bodies in electron microscopy supports the diagnosis of AD. Gillespie et al 3 demonstrated that AD is a lethal pulmonary malformation which is accompanies other renal anomalies as an association. Moerman et al 4 has reported a family with 2 female infants having severe primary pulmonary hypoplasia diagnosed as AD. He concludes the presence of an autosomal recessive mode of inheritance of agene critical of normal lung parenchymal development. Similar conclusion of familial inheritance we reported by Al-Senan et al 5. We believe full term babies with unexplained progressive respiratory distress from birth and progress on, an open lung biopsy should be considered to differentiate between these three main diagnostic challenges and to guide the physician for any further genetic counselling will be helpful to the family.