From Cystic Lung Lesions to Pulmonary Lymphangioleiomyomatosis: A Case-Based Diagnostic and Therapeutic Approach

Background Lymphangioleiomyomatosis (LAM) is a rare, progressive cystic lung disease that primarily affects women of reproductive age. It arises from abnormal proliferation of smooth muscle-like cells, resulting in cystic lung remodeling, impaired airflow, and recurrent pneumothorax. Serum vascular endothelial growth factor D (VEGF-D) can support diagnosis, but normal levels do not exclude the disease. Case presentation We describe a 37-year-old woman with six months of progressive dyspnea and hypoxia (SaO₂: 86%). High-resolution CT revealed diffuse, thin-walled cystic lesions. VEGF-D levels were within the normal range. Pulmonary function tests showed moderate obstructive impairment (FEV₁ 61%, FEV₁/FVC: 64%) and reduced diffusing capacity (DLCO: 45%). Transbronchial lung biopsy confirmed LAM with HMB-45 positivity. Sirolimus therapy was initiated in response to symptomatic impairment. Conclusion This case shows that normal VEGF-D levels do not rule out LAM. Histopathologic confirmation remains essential when clinical and imaging findings are suggestive. Timely diagnosis enables initiation of mTOR inhibitor therapy, which can help stabilize lung function, manage cystic lesions, and inform decisions about further interventions, including lung transplantation.