A40-15 Diffuse Cystic Lung Disease in a Patient With Ankylosing Spondylitis

Abstract Background Ankylosing Spondylitis (AS) is an inflammatory spondyloarthropathy associated with HLA-B27 that may lead to serious pulmonary disease. Classically, pulmonary manifestations have been attributed to reduced chest wall compliance seen in AS, however, pleura-parenchymal lung diseases like Apical Fibro-bullous Disease (AFBD) have been linked to AS. As the list of associated lung findings associated with AS grows, it is important to rule out other diagnoses potentially masquerading as AS-related lung changes including Mycobacterium infections and diffuse cystic lung diseases like Lymphangioleiomyomatosis (LAM). We present a case of idiopathic diffuse cystic lung disease in a 20-year-old female with Ankylosing Spondylitis. Case Presentation A 20-year-old female with HLA-B27 positive ankylosing spondylitis well controlled on Adalimumab presented for initial evaluation of diffuse lung cysts and recurrent spontaneous, non-catamenial pneumothoraxes. She had never smoked or vaped and was a college student. Her family history was negative for pulmonary or autoimmune problems. At the time of evaluation, she denied shortness of breath, chest pain, cough, or wheeze. On exam, SpO2 was 99% breathing ambient air; she was well appearing, and her pulmonary exam was normal. The patient underwent extensive serologic, imaging, and tissue workup including normal VEGFD level, folliculin, TSH1 and TSH2 genetic testing, and normal autoimmune labs. PFTs were significant for a mildly reduced DLCO. Computed tomography with contrast demonstrated a small right pneumothorax and scattered subcentimeter pulmonary cysts. VATS-lung biopsy specimens were negative for HMB (LAM) and CD1a staining (PLCH). The patient was continued on her Adalimumab, counseled on avoiding activities at risk for barotrauma, and was scheduled for yearly HRCT and PFTs. Discussion Cystic lung disease is known to occur with ankylosing spondylitis; however, it is typically associated with fibrotic changes and confined to the upper lobes, as in AFBD. We diagnosed this patient with AS-related idiopathic diffuse cystic lung disease after an exhaustive, yet negative cystic lung disease workup, including a surgical lung biopsy without evidence of inflammatory cells or fibrosis. It was traditionally thought that extra-axial pulmonary manifestations of AS occurred late into its disease course, however this case supports more recent evidence of HRCT revealing underlying lung changes earlier in the AS disease course, even when clinically silent. This abstract is funded by: None