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Congenital pulmonary airway malformation

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Congenital pulmonary airway malformation

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Congenital pulmonary airway malformation

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Content Reviewers:

Rishi Desai, MD, MPH

Contributors:

Tanner Marshall, MS

A congenital pulmonary airway malformation, abbreviated CPAM, is a lung malformation that usually affects a single lobe of one of the lungs, and forms during fetal development.

The old name for CPAMs was congenital cystic adenomatoid malformation, because they have both “cysts” and “glands” in them, but are terribly malformed and disorganized.

CPAM cysts are continuous with the airways, so they’re filled with fluid in utero, and become filled with air after birth.

The cause of CPAMs isn’t known.

It isn’t even known whether they’re a developmental failure or if they’re a type of hamartoma, which is a benign overgrowth of tissue.

Sometimes, the growing CPAM can prevent normal healthy lung tissue from developing - causing pulmonary hypoplasia - which is underdevelopment of the lungs.

Also, a CPAM can push on the heart or large veins, causing blood to back up throughout the fetus’s veins.

When that happens, fluid can start to leak into the fetal tissues, a condition called fetal hydrops.

Whether or not any of this happens largely depends on the size and location of the CPAM.

CPAMs can arise from different spots along the tracheobronchial tree, and that’s how they’re sub-typed.

The five subtypes are named 0 through 4, with type 0 arising from the most proximal airways – the trachea and proximal bronchioles, and type 4 developing all the way down in the alveolus.

Type 0 CPAMs develop at the trachea or proximal bronchus with small cysts, but are pretty rare.

Type 1 CPAMs, which develop in the distal bronchi and proximal bronchioles, are the most common, and have one or more large cysts, with tissue like cartilage in between the cysts.

Type 2’s come from the terminal bronchioles and have smaller cysts.

Summary
Congenital pulmonary airway malformation (CPAM) is a congenital disorder of the lung similar to bronchopulmonary sequestration. In CPAM, usually an entire lobe of lung is replaced by a non-working cystic piece of abnormal lung tissue. This abnormal tissue will never function as normal lung tissue. The underlying cause for CPAM is unknown. 
Sources
  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Pathomechanisms of Congenital Cystic Lung Diseases: Focus on Congenital Cystic Adenomatoid Malformation and Pleuropulmonary Blastoma" Paediatric Respiratory Reviews (2016)
  6. "Congenital Pulmonary Airway Malformation: A Case Report and Review of the Literature" Respiratory Care (2011)