Objective Dermatomyositis (DM) and polymyositis (PM) are systemic autoimmune diseases that have been associated with high in-hospital mortality (IHM). The aim of this study was to use the National Inpatient Sample (NIS), a large US population database, to determine the reasons for hospitalization and IHM in patients with DM and PM. Methods We conducted a medical records review of adult DM/PM hospitalizations in 2016 and 2017 in acute care hospitals across the United States using the NIS. The reasons for IHM and reasons for hospitalization were divided into 19 broad categories based on their principal International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10) diagnosis. Results A total of 27,140 hospitalizations carried either a principal or secondary ICD-10 code for DM or PM. The main reasons for hospitalization were rheumatologic (22%, n = 6085), cardiovascular (15%, n = 3945), infectious (13%, n = 3515), respiratory (12%, n = 3170), and gastrointestinal, (8%, n = 2150). A total of 3.5% of all patients experienced IHM. Infectious (34%, n = 325), respiratory (23%, n = 215), and cardiovascular (15%, n = 140) diagnoses were the most common reasons for IHM. Sepsis ICD-10 A41.9 was the most frequent specific principal diagnosis for both hospitalizations and IHM. Conclusions Our analysis demonstrated that in the NIS the most common reasons for hospitalization in patients with DM/PM were rheumatologic diagnoses. However, IHM in these patients was most frequently from infectious diagnoses, highlighting the need for increased attention to infectious complications in these patients.
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