Answer of November 2016

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Clinical History:

A 59-year-old lady presented with shortness of breath. She was a non-smoker. Patient’s brother and sister had history of pneumothoraces. Patient’s brother also had CT thorax done previously showing bilateral lung cysts. CXR and CT thorax were performed.

Initial CXR

CXR after insertion and removal of chest drain

Non-contrast CT thorax

Diagnosis:

Birt-Hogg-Dube Syndrome

 

Discussion:

Initial CXR shows a large left pneumothorax with mild mediastinal shift towards the right side. A large cystic lesion is seen in medial right lower zone.

 

Subsequent CXR after chest drain better illustrates the large cystic lesion in medial right lower zone with slightly thickened wall.

 

Non-contrast CT thorax shows left hydropneumothorax with subcutaneous emphysema. There are multiple oval or lentiform thin-walled cysts of various sizes in both lungs with lower zonal predominance. Apparent wall thickening of the largest cyst in medial basal segment of right lower lobe is likely due to compressive collapse of adjacent lung parenchyma. No lung nodule or ground-glass opacity is seen.

 

Differential diagnoses of cystic lung disease include Langerhan’s cell histiocytosis (LCH), lymphangioleiomyomatosis (LAM), neurofibromatosis type 1 (NF1) and lymphocytic interstitial pneumonitis (LIP).

 

Langerhan’s cell histiocytosis (LCH) usually occurs in young adults with smoking history. The cysts are of bizarre shapes. There will also be centrilobular nodules and reticular densities/ thickening of interlobular septa in the lung.

 

Lymphangioleiomyomatosis (LAM) usually affect women of child-bearing age. Thin-walled cysts of similar sizes are usually seen throughout the lung without zonal predominance.

 

Pulmonary manifestations of neurofibromatosis type 1 consist of peripheral nodules, lower zone fibrosis and upper zone large bullae.

 

Lymphocytic interstitial pneumonitis (LIP) has features including perivascular thin-walled cysts, ill-defined centrilobular nodules, ground-glass opacities and interlobular septal thickening.

 

The features of HRCT in this case together with the familial history of cystic lung disease are highly suggestive of the diagnosis of Birt-Hogg-Dube Syndrome. This case was subsequently confirmed by genetic testing.