Congenital high airway obstruction syndrome
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- updated 15 Jul 2022:
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Congenital high airway obstruction syndrome or sequence (CHAOS)refers to a rare, often lethal, congenital laryngotracheal condition and is primarily characterised by obstruction to the fetal upper airway.
Epidemiology
Associations
Pathology
CHAOS can be of three possible types 2:
complete laryngeal atresia without an oesophageal fistula
complete laryngeal atresia with a tracheo-oesophageal fistula
near-complete high upper airway obstruction
Associations
Radiographic features
Antenatal ultrasound
Ultrasound may show some or all of the following features 4,5:
dilated trachea/bronchi: distal to the obstruction
enlarged
andechogenic lungsdiaphragmatic inversion and/or flattening
-
presence of the fetal heart may appear displaced to the midline and compressed
Ancillary sonographic features include:
-
presence of -
presence of
Fetal MRl
May confirm features detected on ultrasound as well as more accurately show the level of obstruction. Lung signal is increased 5.
Treatment and prognosis
The prenatal natural history and postnatal course of CHAOS often depend on whether the airway obstruction is complete. An ex utero intrapartum treatment (EXIT) procedure may offer potential for salvage 1,3. Overall prognosis is considered generally poor 6.
Differential diagnosis
The differential diagnosis of echogenic fetal lung is congenital cystic adenomatoidpulmonary airway malformation (CCAM(CPAM) type III. In CHAOS, both lungs are echogenic, whereas CCAMCPAM is usually unilateral, but can be bilateral in rare cases. Dilated airway is another clue whichthat is seen only in CHAOS 9-11.
See also
-<p><strong>Congenital high airway obstruction syndrome </strong>or <strong>sequence </strong>(<strong>CHAOS</strong>)<strong> </strong>refers to a rare, often lethal, congenital laryngotracheal condition and is primarily characterised by obstruction to the fetal upper airway.</p><h4>Pathology</h4><p>CHAOS can be of three possible types <sup>2</sup>:</p><ul>-<li>complete <a href="/articles/laryngeal-atresia">laryngeal atresia</a> without an oesophageal fistula</li>-<li>complete <a href="/articles/laryngeal-atresia">laryngeal atresia</a> with a <a href="/articles/congenital-tracheo-oesophageal-fistula">tracheo-oesophageal fistula</a>-</li>-<li>near-complete high upper airway obstruction </li>-</ul><h5>Associations</h5><ul><li><a href="/articles/fraser-syndrome">Fraser syndrome</a></li></ul><h4>Radiographic features</h4><h5>Antenatal ultrasound</h5><p>Ultrasound may show some or all of the following features <sup>4,5</sup></p><ul>-<li>dilated trachea/bronchi: distal to the obstruction</li>-<li>enlarged and echogenic lungs</li>-<li>diaphragmatic inversion and/or flattening</li>-<li>presence of <a href="/articles/fetal-ascites">fetal ascites</a>-</li>-<li>the fetal heart may appear displaced to the midline and compressed</li>-</ul><p>Ancillary sonographic features include</p><ul>-<li>presence of <a href="/articles/fetal-anasarca">fetal anasarca</a> <sup>7</sup>-</li>-<li>presence of <a href="/articles/polyhydramnios">polyhydramnios</a> <sup>5</sup>-</li>-</ul><h5>Fetal MRl</h5><p>May confirm features detected on ultrasound as well as more accurately show the level of obstruction. Lung signal is increased <sup>5</sup>. </p><h4>Treatment and prognosis</h4><p>The prenatal natural history and postnatal course of CHAOS often depend on whether the airway obstruction is complete. An <a href="/articles/ex-utero-intrapartum-treatment-exit-procedure">ex utero intrapartum treatment (EXIT) procedure</a> may offer potential for salvage <sup>1,3</sup>. Overall prognosis is considered generally poor <sup>6</sup>.</p><h4>Differential diagnosis</h4><p>The differential diagnosis of echogenic fetal lung is <a href="/articles/congenital-pulmonary-airway-malformation">congenital cystic adenomatoid malformation (CCAM)</a> type III. In CHAOS, both lungs are echogenic, whereas CCAM is usually unilateral, but can be bilateral in rare cases. Dilated airway is another clue which is seen only in CHAOS <sup>9-11</sup>.</p><h4>See also</h4><ul><li><a href="/articles/tracheal-atresia">tracheal atresia</a></li></ul>- +<p><strong>Congenital high airway obstruction syndrome </strong>or <strong>sequence </strong>(<strong>CHAOS</strong>)<strong> </strong>refers to a rare, often lethal, congenital laryngotracheal condition and is primarily characterised by obstruction to the fetal upper airway.</p><h4>Epidemiology</h4><h5>Associations</h5><ul><li><p><a href="/articles/fraser-syndrome">Fraser syndrome</a></p></li></ul><h4>Pathology</h4><p>CHAOS can be of three possible types <sup>2</sup>:</p><ul>
- +<li><p>complete <a href="/articles/laryngeal-atresia">laryngeal atresia</a> without an oesophageal fistula</p></li>
- +<li><p>complete <a href="/articles/laryngeal-atresia">laryngeal atresia</a> with a <a href="/articles/congenital-tracheo-oesophageal-fistula">tracheo-oesophageal fistula</a></p></li>
- +<li><p>near-complete high upper airway obstruction </p></li>
- +</ul><h4>Radiographic features</h4><h5>Antenatal ultrasound</h5><p>Ultrasound may show some or all of the following features <sup>4,5</sup>:</p><ul>
- +<li><p>dilated trachea/bronchi: distal to the obstruction</p></li>
- +<li><p>enlarged <a href="/articles/echogenic-fetal-lung-lesions" title="Echogenic lung lesions in utero">echogenic lungs</a></p></li>
- +<li><p>diaphragmatic inversion and/or flattening</p></li>
- +<li><p><a href="/articles/fetal-ascites">fetal ascites</a></p></li>
- +<li><p>the fetal heart may appear displaced to the midline and compressed</p></li>
- +</ul><p>Ancillary sonographic features include:</p><ul>
- +<li><p><a href="/articles/fetal-anasarca">fetal anasarca</a> <sup>7</sup></p></li>
- +<li><p><a href="/articles/polyhydramnios">polyhydramnios</a> <sup>5</sup></p></li>
- +</ul><h5>Fetal MRl</h5><p>May confirm features detected on ultrasound as well as more accurately show the level of obstruction. Lung signal is increased <sup>5</sup>. </p><h4>Treatment and prognosis</h4><p>The prenatal natural history and postnatal course of CHAOS often depend on whether the airway obstruction is complete. An <a href="/articles/ex-utero-intrapartum-treatment-exit-procedure">ex utero intrapartum treatment (EXIT) procedure</a> may offer potential for salvage <sup>1,3</sup>. Overall prognosis is considered generally poor <sup>6</sup>.</p><h4>Differential diagnosis</h4><p>The differential diagnosis of <a href="/articles/echogenic-fetal-lung-lesions" title="Echogenic fetal lung lesions">echogenic fetal lung</a> is <a href="/articles/congenital-pulmonary-airway-malformation">congenital pulmonary airway malformation (CPAM)</a> type III. In CHAOS, both lungs are echogenic, whereas CPAM is usually unilateral, but can be bilateral in rare cases. Dilated airway is another clue that is seen only in CHAOS <sup>9-11</sup>.</p><h4>See also</h4><ul><li><p><a href="/articles/tracheal-atresia">tracheal atresia</a></p></li></ul>
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