What Is ACD?
Alveolar Capillary Dysplasia is a rare, typically fatal congenital diffuse lung disease. It is characterized by abnormally developed alveoli along with pulmonary vessels that are misaligned that cause highly elevated pulmonary pressure. Due to the structural abnormalities, it creates an inability to effectively oxygenate and remove carbon dioxide from the blood.
Presentation
ACD typically presents in newborn babies within minutes to hours after birth as rapid and labored breathing, blue-colored lips or skin, and unequal pre and post oxygenation levels. These symptoms quickly lead to respiratory failure and death. Atypical forms of ACD have been reported with initially milder symptoms and survival of many months before the onset of respiratory failure or lung transplantation.
Causes
ACD is considered an autosomal dominant disorder, typically caused by mutations or deletions affecting the FoxF1 gene (Chromosome 16) or its nearby enhancer region. Evidence strongly suggests that the FOXF1 regulatory region is imprinted, which might affect disease severity and may permit some to carry the disease with few or no symptoms. Exactly how these mutations lead to abnormal lung development is unknown.
Diagnosis
ACD is typically diagnosed by examination of lung tissue under a microscope, either from lung biopsy or through autopsy. The characteristic findings of misplaced pulmonary veins adjacent to pulmonary arteries, and abnormal alveolar and capillary development confirm the diagnosis. FOXF1 genetic testing is also available, which can confirm the diagnosis without invasive testing.
Treatment
There are no effective treatments for severe ACD. Standard therapy, which includes mechanical ventilation, pulmonary vasodilators, and possibly ECMO, only provides temporary improvement in symptoms with disease progression returning within hours. Most of those affected with ACD do not live past four to six weeks of age. For babies with atypical ACD, response to medical therapy is more sustained, lasting for several months. For those that can be stabilized, definitive treatment is bilateral lung transplantation.