Pediatric Pulmonary Hypoplasia Clinical Presentation

Updated: Aug 11, 2017
  • Author: Terry W Chin, MD, PhD; Chief Editor: Girish D Sharma, MD, FCCP, FAAP  more...
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There is wide variation in the clinical presentation of pulmonary hypoplasia, depending on the extent of hypoplasia and other associated anomalies. [16]

The history may include poor fetal movement or amniotic fluid leakage and oligohydramnios. The neonate may be asymptomatic or may present with severe respiratory distress or apnea that requires extensive ventilatory support. In older children, dyspnea and cyanosis may be present upon exertion, or a history of repeated respiratory infections may be noted.



The external chest may appear normal or may be small and bell shaped, with or without scoliosis. A mediastinal shift is observed toward the involved side, and dullness upon percussion is heard over the displaced heart. In right-sided hypoplasia, the heart is displaced to the right, which may lead to a mistaken diagnosis of dextrocardia. Breath sounds may be decreased or absent on the side of hypoplasia, especially over the bases and axilla.

Some infants may present with otherwise asymptomatic tachypnea, and other may have severe respiratory distress at birth requiring ventilatory support. Pneumothorax, either spontaneous or associated with mechanical ventilation, may occur.

Infants with secondary pulmonary hypoplasia may have associated congenital anomalies or features suggestive of neuromuscular diseases. Such patients may have myopathic facies, with a V-shaped mouth, muscle weakness, and growth restriction. Multiple genetic syndromes associated with primary pulmonary hypoplasia are reported in the literature such as Scimitar Syndrome, Trisomy 21, and Pena-Shokeir Syndrome (fetal akinesia). [28, 29]  

Compression deformities due to prolonged oligohydramnios, contractures, and arthrogryposis may be present. The Potter facies (hypertelorism, epicanthus, retrognathia, depressed nasal bridge, low set ears) suggest the possibility of lung hypoplasia caused by the associated renal defects.

Abdominal masses, such as cystic renal diseases and an enlarged bladder, must be sought. Associated anomalies of the cardiovascular, gastrointestinal (eg, tracheoesophageal fistula, imperforate anus, communicating bronchopulmonary foregut malformation), and genitourinary systems, as well as skeletal anomalies of the vertebrae, thoracic cage, and upper limbs, may be found upon examination. [30]



The causes of primary pulmonary hypoplasia have not been identified. As mentioned above, Sonic hedgehog (Shh) appears to play a role in pulmonary branching morphogenesis. Shh knockout transgenic mice had severely hypoplastic lungs with loss of cartilaginous rings. [9, 11] Experimental models suggest deficiencies in certain factors and/or their receptors can result in abnormal lung growth (see Table 1). These findings suggest that primary pulmonary hypoplasia likely results from disruptions in signaling during embryologic phase of lung development but needs further study.

Causes of secondary pulmonary hypoplasia include conditions that can result in small fetal thoracic volume, prolonged oligohydramnios, decreased fetal breathing movements, and congenital heart disease with poor pulmonary blood flow (see Table 2). Condition such as congenital diaphragmatic hernia, large pleural effusions and congenital pulmonary malformations also lead to the development of pulmonary hypoplasia due to mass effect. [1]


Table 1. Factors and/or Their Receptors Possibly Involved with Abnormal Lung Growth (Open Table in a new window)

Transcription Factors

Growth Factors

Thyroid transcription factor-1 (TTF-1) [12]

Vascular endothelial growth factor receptors (VEGFR1 and VEGFR2) [15]

GATA-4 [20]

Insulinlike growth factors (IGF-1 and IGF-2) and their receptors (IGF-1R and IGF-2R) [18]

FOG-2 [23]

Epidermal growth factors and its receptor family (eg, ErbB receptors) [21]

Hepatocyte nuclear factor (HNF3ß10)

Mitogen-activated protein kinases


Connective tissue growth factor [31]


Table 2. Causes of Secondary Pulmonary Hypoplasia (Open Table in a new window)

Small Fetal Thoracic Volume

Prolonged Oligohydramnios

Decreased Fetal Breathing Movements

Congenital Heart Diseases With Poor Pulmonary Blood Flow


Fetal renal agenesis

Central nervous system (CNS) lesions

Tetralogy of Fallot

Cystic adenomatoid malformation (CAM)

Urinary tract obstruction

Lesions of the spinal cord, brain stem, and phrenic nerve

Hypoplastic right heart

Pulmonary sequestration

Bilateral renal dysplasia

Neuromuscular diseases (eg, myotonic dystrophy, spinal muscular atrophy)

Pulmonary artery hypoplasia

Pleural effusions with fetal hydrops, hydrothorax

Bilateral cystic kidneys

Arthrogryposis multiplex congenital secondary to fetal akinesia

Scimitar syndrome causing a unilateral right-sided pulmonary hypoplasia

Thoracic neuroblastomas

Prolonged rupture of membranes (PROM)

Maternal depressant drugs

Trisomies 18 and 21

Malformations of the thorax (eg, asphyxiating thoracic dystrophy)

Premature PROM



Diaphragmatic anomalies (eg, abdominal wall defects, eventration of the diaphragm)

Potter syndrome



Musculoskeletal disorders (eg, achondroplasia, thanatophoric dysplasia, osteogenesis imperfecta)




Abdominal masses causing compression