Alveolar capillary dysplasia with misalignment of pulmonary veins

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a disorder affecting the development of the lungs and their blood vessels. The disorder affects the millions of small air sacs (alveoli) in the lungs and the tiny blood vessels (capillaries) in the alveoli. It is through these alveolar capillaries that inhaled oxygen enters the bloodstream for distribution throughout the body and carbon dioxide leaves the bloodstream to be exhaled.

In ACD/MPV, the alveolar capillaries fail to develop normally. The number of capillaries is drastically reduced, and existing capillaries are improperly positioned within the walls of the alveoli. These abnormalities in capillary number and location impede the exchange of oxygen and carbon dioxide.

Other abnormalities of the blood vessels in the lungs also occur in ACD/MPV. The veins that carry blood from the lungs into the heart (pulmonary veins) are improperly positioned and may be abnormally bundled together with arteries that carry blood from the heart to the lungs (pulmonary arteries). The muscle tissue in the walls of the pulmonary arteries may be overgrown, resulting in thicker artery walls and a narrower channel. These changes restrict normal blood flow, which causes high blood pressure in the pulmonary arteries (pulmonary hypertension) and requires the heart to pump harder.

Most infants with ACD/MPV are born with additional abnormalities. These may include abnormal twisting (malrotation) of the large intestine or other malformations of the gastrointestinal tract. Cardiovascular and genitourinary abnormalities are also common in affected individuals.

Infants with ACD/MPV typically develop respiratory distress within a few minutes to a few hours after birth. They experience shortness of breath and cyanosis, which is a bluish appearance of the skin, mucous membranes, or the area underneath the fingernails caused by a lack of oxygen in the blood. Without lung transplantation, infants with ACD/MPV have not been known to survive past one year of age, and most affected infants live only a few weeks.