SESSION TITLE: Tuesday Fellows Case Report Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM INTRODUCTION: Pulmonary Langerhan’s Histiocytosis (PLCH) has been described previously as a nodular and cystic interstitial lung disease most commonly seen in adults aged 20-40 years old. Up to 90% of patients diagnosed with PLCH are smokers.1 The disease is believed to progress despite smoking cessation due to a BRAF-V600E mutation.2 Only 15% of reported cases present with recurrent pneumothorax.3 Here we present a case of a young smoker with PLCH with 3 separate pneumothoraces. CASE PRESENTATION: Our patient is a 35-year-old male with no significant PMH who presented to an outside ER for acute onset chest pain and SOB. He noted a sharp, severe, constant pain, worse with inspiration. The next morning, he was unable to walk due to chest pain and was brought to the ER. He was noted to have a 50% pneumothorax on the left apex and a chest tube was placed. He was transferred to our facility for higher level of care. The year earlier he had a cholecystectomy and CT had noted minimal cystic changes at the bases of the lungs bilaterally, but he never followed up with a Pulmonologist for this (Figure 1). The patient denied any SOB, wheezing, or hemoptysis. He did have an occasional productive cough after smoking. He had quit smoking six months prior but had a 10-pack year history. He denied any occupational exposures, recent travel, animal exposure, or recent illness. Alpha-1 antitrypsin level was elevated at 214, CK within normal limits. He had negative RF, CCP, ANA, anti-SSB, anti-SSA, Scl-70. HIV screen was negative. On day 2 he had VATS-assisted biopsies from the left upper and lower lung. Tissue culture noted many WBC, few gram-negative rods by gram stain. He was treated empirically with Ceftriaxone. The patient developed a second right-sided and third left-sided spontaneous pneumothorax requiring bilateral chest tubes until day 10 post-op. Surgical pathology noted scars, mostly peribronchiolar, distorted architecture with eosinophils and elongate cells. Immunostains confirmed S100 positivity. Consultation was obtained from Mayo Clinic in Arizona and their lab confirmed cells in a pattern of fibrosis notable for extensive collections of histiocytes diffusely positive for CD1a, focally positive for S100. No granulomas were seen. He was ultimately referred to University of Colorado for transplant evaluation. At follow up he was noted to be doing well and did not require oxygen supplementation. DISCUSSION: Rapid diagnosis of PLCH is necessary to prevent secondary pulmonary hypertension and prompt smoking cessation should be encouraged. CONCLUSIONS: While treatment with immunosuppressants, cladarabine, and corticosteroids have been reported in some cases, treatment remains controversial. Some patients progress to a point of needing lung transplant and early referral to a transplant center needs to be considered. Reference #1: Vasallo R, Ryu JH, Schroeder DR, Decker PA, Limper AH. Clinical outcomes of pulmonary Langerhans’ cell histiocytosis in adults. NEJM 2002; 346 (7): 484-490. Reference #2: Kamionek M, Ahmadi P, Sakhdari A. Mutually exclusive extracellular signal regulated kinase pathway mutations are present in different stages of multifocal pulmonary Langerhans cell histiocytosis supporting the clonal nature of the disease. Histopathology. 2016;69(3):,499-509. Reference #3: Mendez JL, Nadrous HF, Vasallo R, Decker P, Ryu JH. Pneumothorax in pulmonary Langerhans cell histiocytosis. Chest. 2004; 125 (3):1028-1032. DISCLOSURES: My spouse/partner as a Speaker/Speaker's relationship with Salix Please note: $1001 - $5000 Added 03/13/2019 by Ebtesam Islam, source=Web Response, value=Speaker fee No relevant relationships by Ximena Solis, source=Web Response No relevant relationships by Wasawat Vutthikraivit, source=Web Response