This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Interstitial Lung Disease, Subject name: Medicine
A 25-year-old female presents with progressive dyspnea for one year. CXR shows interstitial opacities and spirometry shows an obstructive pattern. What is the diagnosis? 
Select and explain. 
A. Non-specific interstitial pneumonitis, B. Pulmonary Lymphangioleiomyomatosis, C. Idiopathic pulmonary fibrosis, D. Pulmonary Alveolar Proteinosis
B: Pulmonary Lymphangioleiomyomatosis
Answer: B: Pulmonary Lymphangioleiomyomatosis 
Explanation: Interstitial lung disease leads to the restrictive pattern on spirometry. However tuberous sclerosis and Lymphangioleiomyomatosis are exceptions and lead to an obstructive pattern. Pulmonary LAM presents in young females with emphysema, recurrent pneumothorax and chylous pleural effusion.