CYSTIC ADENOMATOID MALFORMATION
 
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CYSTIC ADENOMATOID MALFORMATION

 

DEFINITION:

A congenital anomaly of the lung characterized by congenital cysts and respiratory distress on the first day of life.

EPIDEMIOLOGY:

  • incidence: accounts for about 25% of congenital lung malformations
  • age of onset:
    • 1st day: 68% (CAM can be detected as early as 18 wks in
    • 2-7 days: 5% utero by imaging studies)
    • 8 days: 27%
  • risk factors:
    • M > F

PATHOGENESIS:

1. Background

  • adenomatoid (normal tissue but put together improperly) over-growth of pulmonary tissue in the region of the end bronchioles with suppression of alveolar growth

2. History

  • 1949 - Chin and Tang
    • first to describe CAM
    • clinical classification
  • 1977 - Stocker
    • first to divide CAM into 3 types based on cyst size
    • pathological classification

3. Types*

1. Cystic

  • 75% of cases
  • large cysts (mean = 7 cm in diameter) or a single dominant cyst surrounded by smaller cysts
  • often accompanied by a mediastinal shift
  • good prognosis

2. Mixed

  • 10-15% of cases
  • many small cysts (1-2 cm)
  • mediastinal shift less common
  • poor prognosis

3. Solid

  • 10% of cases
  • mass of microcysts (< 1 mm)
  • predilection for the lower lobes
  • associated with anasarca, stillbirth, and severe respira-tory distress
  • poor prognosis
  • *based on Beluffi et al., (1989)

    • 4. Differential Diagnosis

    • congenital diaphragmatic hernia
    • congenital lobar emphysema
    • congenital/acquired cystic disease
    • post-staph pneumatocoeles
    • pulmonary sequestration

    CLINICAL FEATURES:

    1. Respiratory Manifestations

    • respiratory distress (73%)
    • stillbirth (17%)
    • indolent respiratory infections with chronic cough (10%)

    2. Complications

    • anasarca - polyhydramnios
    • hydrops - Potter's Syndrome
    • jejunal atresia - prematurity
    • pneumonia

    INVESTIGATIONS:

    1. Imaging Studies

    1. Chest X-Ray

    • three patterns
      • 73% - multicentric with cyst expansion and mediastinal shift
      • 13% - dominant cyst with multicystic background
      • 13% - solid homogeneous mass
    • usually only one lobe affected and the LLL most commonly involved
    • complications on x-ray: air-fluid levels, anterior media-stinal herniation, diaphragmatic herniation, hypoplastic lungs, pneumonia, pneumothorax, persistant pulmonary hyper-tension
    • radiographic study of the abdomen is important to rule out congenital diaphragmatic herniation

    2. CT/MRI

    • CT appearance in neonates and infants may show large masses containing multiple, large, thin-walled cysts displacing the mediastinum

    MANAGEMENT:

    1. Supportive

    • respiratory distress with ventilation, ECMO

    2. Surgery

    • lobectomy vs pneumonectomy

     

     

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