PULMONARY ROCKS! A CASE OF PULMONARY ALVEOLAR MICROLITHIASIS

Abstract

TOPIC: Diffuse Lung Disease TYPE: Fellow Case Reports INTRODUCTION: Pulmonary alveolar microlithiasis (PAM) is an extremely rare lung disease characterized by the development of calcium phosphate deposits (microliths) within the alveolar spaces. Genetic mutations in the SLC34A2 gene (solute carrier family 34 member 2 gene), which encodes for a sodium-phosphate co-transporter, have been described as the cause of the disease. This co-transporter is located on type II alveolar pneumocytes and is responsible for removing phosphate ions from the alveolar space. Without effective transport, phosphate ions bind to calcium ions leading to calcium phosphate deposits within the alveoli. Over time this often leads to pulmonary fibrosis and progressive respiratory failure. Here, we present a case of pulmonary alveolar microlithiasis that was initially suspected to be metastatic endometrial carcinoma. CASE PRESENTATION: A 37-year-old female presented to gynecology clinic for evaluation of abnormal uterine bleeding. Endometrial biopsy showed endometrioid adenocarcinoma of the uterus. Staging CT scans revealed bilateral adnexal masses, metastatic disease in the liver, peritoneal carcinomatosis, and concern for lymphangitic carcinomatosis in the lungs due to calcification of the pleura and diaphragm. Liver biopsy confirmed metastatic disease of ovarian primary consistent with synchronous stage IV ovarian cancer. She underwent chemotherapy with carboplatin and paclitaxel as well as abdominal hysterectomy and debulking surgery with good response; however, repeat CT chest showed persistent pulmonary disease with innumerable calcified micronodules and extensive pleural, fissural, and interlobular calcifications. Transbronchial biopsies were obtained and revealed diffuse intra-alveolar laminated concentric deposits consistent with microliths and diagnostic of pulmonary alveolar microlithiasis. At the time of diagnosis her pulmonary function testing showed mild restriction. She has no family history of pulmonary disease and had no pulmonary symptoms. Calcium supplements were discontinued, and she was treated with a low phosphorus diet. She continues to undergo monitoring for the development of symptoms as well as monitoring of her pulmonary function. DISCUSSION: PAM is an extremely rare genetic disease caused by a defective sodium-phosphate co-transporter that leads to the accumulation of microliths within the alveolar spaces. Pulmonary fibrosis and progressive respiratory failure is the typical cause of death, although the rate of progression is variable. There is no known effective treatment except for lung transplant. A low phosphorus diet, bisphosphonates, and repeated bronchoalveolar lavage have been studied without clear clinical benefit. CONCLUSIONS: (See Discussion) REFERENCE #1: Castellana G, Castellana G, Gentile M, Castellana R, Resta O. Pulmonary alveolar microlithiasis: review of the 1022 cases reported worldwide. Eur Respir Rev. 2015 Dec;24(138):607-20. REFERENCE #2: Saito A, McCormack FX. Pulmonary Alveolar Microlithiasis. Clin Chest Med. 2016;37(3):441-448. doi:10.1016/j.ccm.2016.04.007. DISCLOSURES: No relevant relationships by Carlos Cardenas, source=Web Response No relevant relationships by Sakda Sathirareuangchai, source=Web Response No relevant relationships by Andrew Tomlinson, source=Web Response