SESSION TITLE: Medical Student/Resident Pulmonary Manifestations of Systemic Disease 3 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: Pulmonary Langerhans cell histiocytosis (PLCH) is a rare, diffuse interstitial lung disease occurring in young adults who smoke cigarettes. It is characterized by bronchiolocentric nodules and/or cysts in upper and mid lung distribution that spare the costophrenic angles. The true incidence and prevalence is unknown but diagnosed in less than 5 percent of lung biopsies and thought to account for 3-5% of adult lung disease [1]. The pathophysiology is not fully understood but thought to involve CD1 antigen positive Langerhans cells of dendritic and macrophage origin. CASE PRESENTATION: A 37-year-old Caucasian female with no PMH presented with cough, wheeze, and shortness of breath to her PCP. She was diagnosed with atypical pneumonia and treated with azithromycin. She continued to have symptoms one month later and was diagnosed with influenza. She was then diagnosed with bronchitis and treated with steroids. During these episodes she received chest x-rays with opacities, attributed to infection. Follow up imaging remained abnormal. A CT chest without contrast was obtained 3 months after initial presentation, with multiple irregularly shaped thin walled cysts and nodules in the upper lobes sparing costophrenic angles. Classic findings for PLCH (Image 1). PFTs were normal. Notably the patient had an extensive smoking history, 15 pack years. She was able to quit successfully with help from PCP after CT scan.At follow up, patient denied cough, shortness of breath, PFTs and physical exam were normal. The patient was sent home with plans for follow up CT in one month after extended period of smoking cessation. Repeat CT 4 months after initial (Image 2) showed marked interval improvement in thin walled cysts and nodules after continued smoking cessation. Bronchoscopy was deferred at that time due to symptom resolution, improvement in radiography, and normal lung function determined by PFTs. Patient scheduled for follow up X-ray in 6 months. DISCUSSION: Complications of PLCH include pulmonary hypertension, a relatively common and sometimes severe complication, or progressive loss lung function diffusing capacity to the point of needing lung transplantation. Outside of smoking cessation, there is limited data on efficacy of pharmaceuticals such as corticosteroids or immunosuppressants. As more is understood regarding PLCH, further therapies may be developed. 50% of PLCH cases have association with BRAF V600E mutation [2]. F The mitogen-activated protein kinase pathway is known to be activated in LCH lesions regardless of BRAF. PD-1/PDL-1 may also be involved [3]. For the time being, providers should be prescribing pharmaceuticals with caution for patients who are symptomatic or have signs of decreasing pulmonary function. CONCLUSIONS: Cystic lung disease presenting in a young female smoker can be managed by smoking cessation and observation if they are asymptomatic with preserved lung function. Reference #1: Gaensler EA, Carrington CB: Open biopsy for chronic diffuse infiltrative lung disease: clinical, roentgenographic, and physiological correlations in 502 patients. Ann Thorac Surg. 1980, 30 (5): 411-426. 10.1016/S0003-4975(10)61291-X. Reference #2: Badalian-Very G, Vergilio JA, Degar BA, et al. Recurrent BRAF mutations in Langerhans cell histiocytosis. Blood 2010; 116: 1919-1923. Reference #3: Xu J, Sun HH, Fletcher CD, et al. Expression of programmed cell death 1 ligands (PD-L1 and PD-L2) in histiocytic and dendritic cell disorders. Am J Surg Pathol 2016; 40:443-453. DISCLOSURES: no disclosure on file for Rachel Butler; No relevant relationships by Roger Struble, source=Web Response