Failure of the lung to develop to its normal size.
Primary isolated pulmonary hypoplasia is rare. Secondary pulmonary
hypoplasia is more common and occurs in association with congenital
diaphragmatic hernia, oligohydramnios (mostly related to renal dysfunction),
skeletal dysplasias, fetal hydrops, malformations of the central nervous system, and
Isolated primary pulmonary hypoplasia is very rare.
However, conditions such as congenital diaphragmatic hernia are more common
and inevitably associated with pulmonary hypoplasia.
Possibility of autosomal recessive
transmission in the isolated form has been described.
There is a decrease in lung volume and weight and
there is a commensurate decrease in pulmonary function. Microscopic
examination may reveal absent or reduced development of the lungs with a
deficit in any combination of tubular bronchioles, acini, or alveoli,
incapable of significant gas exchange or reduced airway generation, with
fewer and smaller alveoli.
Based on measurement of lung volumes (e.g., whole-body
plethysmography or inert gas dilution method) and the exclusion of other
pathologies that may cause tachypnea. Oligohydramnios is a well-known risk
factor. Chest CT scan or anteand postnatal MRI are presently the diagnostic
tools of choice.
The symptoms depend on the severity of the
hypoplasia. Pulmonary hypoplasia is a (milder) form of pulmonary agenesis
and can occur unilaterally or bilaterally. Whereas unilateral pulmonary
hypoplasia has the same frequency for each side, left-sided lesions have a
much better prognosis. Secondary pulmonary hypoplasia describes a decrease
in intrathoracic volume as a result of extrathoracic compression (e.g.,
oligohydramnios secondary to renal agenesis or dysplasia, congenital
thoracic or skeletal dysplasia causing thoracic constriction and leading to
limited lung development with bilateral pulmonary hypoplasia) or
intrathoracic compression (e.g., congenital diaphragmatic hernia, polycystic
kidney disease [secondary to the large abdominal mass], tumors, congenital
cystic adenomatoid malformation, or large pleural effusions). Furthermore,
there is an association with malformations of the central nervous system (e.g., anencephaly)
and neuromuscular diseases (affecting respiratory muscles/diaphragm). In a
few cases, abnormalities of the face (hemifacial microsomia, dysplastic
ears, torticollis) or jaw (unilateral mandibulofacial dysostosis)
ipsilateral to the side of the pulmonary lesion (if unilateral) have been
described. Anomalies of the extremities (in the majority of cases, the arm
ipsilateral to the lesion) are not uncommon and include ulnar, radial, and
thumb anomalies. Thoracic asymmetry may be associated with vertebral
anomalies. The diaphragm may be high riding on the affected side, but in
contrast to hemidiaphragmatic paralysis, it is not paralyzed and functions
normally. Unilateral pulmonary hypoplasia must be differentiated from other
conditions potentially resulting in mediastinal shift, such as cystic
adenomatoid malformation, diaphragmatic hernia, or bronchopulmonary
The presence of other associated
anomalies should be excluded and the involved system assessed. Facial
dysmorphism and jaw anomalies may result in difficult airway management and
make preoperative airway assessment mandatory. Laboratory investigations
should include a complete blood cell count and arterial blood gas analysis. A preoperative chest
radiograph is strongly recommended and echocardiography should be performed ...