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Lymphangiomyomatosis

Lymphangiomyomatosis (LAM) is a rare multi-system disorder which can occur either sporadically or in association with the tuberous sclerosis (TS) complex-approximately 1% of those with TS. 

Epidemiology

It almost exclusively affects women of child bearing age 7. The estimated incidence is 1:400,000 4.

Pathology

The disease is characterised by persistence of dilated lymphatics and interstitial proliferation of abnormal smooth muscle which in turn can obstruct venules and lymphatics.

In the chest, there are two phases of proliferation in lymphangiomyomatosis. The early phase is characterised by proliferation of immature muscle cells which cover alveolar walls, bronchioles, pleura and vessels, including lymphatic routes. In the late phase there is development of cystic spaces and wider proliferation of muscle cells throughout the lung.

Radiographic features

Lymphangiomyomatosis is a multi-system disorder and can affect many organs. 

Bone 

May show massive osteolysis with little or no periosteal reaction. Often multifocal disease

Chest 

Multiple thin walled cysts throughout the lungs (usually with an uniform distribution). These are present in nearly all cases. If the cysts are small they may be seen as diffuse coarse interstitial markings on plain film.

Additional features 
  • general/plain film:
    • chylothorax: chylous pleural effusion
    • evidence of hyperinflation
    • diffuse bilateral reticulonodular densities
    • recurrent pneumothoraces in complicated cases
  • HRCT:
    • thin walled cysts of variable sizes surrounded by normal lung parenchyma-can be seen throughout  the lung
    • interlobular septal thickening
    • may show a dilated thoracic duct
    • haemorrhages may be seen as areas of increased attenuation 
Abdomen and pelvis:
Neck:

Complications

Thoracic:
  • recurrent pneumothorax: can occur in up to 80% of cases
  • thoracic chylous collections
  • haemoptysis-occasional 4
Abdominal:
  • pelvic lymphatic obstruction

Treatment and prognosis

Despite treatment with agents such as medroxyprogesterone and tamoxifen 6, LAM tends to be progressive with most of disease severity due to pulmonary disease.

Differential diagnosis

For pulmonary manifestations the main differential to be considered is Langerhans cell histiocytosis (LCH) which tends to have a mid to upper lobe distribution with preservation of costophrenic angles. In addition, the cysts in LCH tend to be more irregular in contour. 

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