Background <p>Dermatomyositis (DM) and polymyositis (PM) hospitalizations are frequently complicated by multisystem involvement, contributing to increased healthcare utilization and burden. Whether malnutrition identifies a high-risk inpatient phenotype within DM/PM hospitalizations remains insufficiently characterized.</p> Methods <p>Using the National Inpatient Sample (2016–2022), we included adult hospitalizations with DM/PM. Outcomes included in-hospital mortality, major complications and resource utilization. To reduce confounding, we performed 1:2 propensity score matching using age, sex, race, bed size of hospital, household income quartile, type of insurance, hospital region, teaching status, and elective admission. In the matched cohort, multivariable logistic regression models adjusted for the propensity score and comorbidities were used to estimate odds ratios (ORs) with 95% confidence intervals (CIs).</p> Results <p>Among 18,662 DM/PM hospitalizations, 2,405 (12.9%) had malnutrition. After propensity score matching, malnutrition was associated with higher in-hospital mortality (9.4% vs 4.2%; OR 1.553, 95% CI 1.250–1.931) and was associated with higher odds of septicemia (OR 1.575, 95% CI 1.368–1.813), urinary tract infection (OR 1.362, 95% CI 1.171–1.584), cardiac arrest (OR 1.608, 95% CI 1.082–2.390), aspiration pneumonia (OR 2.969, 95% CI 2.422–3.639), respiratory failure (OR 1.578, 95% CI 1.394–1.787), and acute kidney injury (OR 1.208, 95% CI 1.053–1.386). Malnutrition was also associated with discharge to a post-acute care facility, extended length of stay, and increased total hospital charges.</p> Conclusions <p>In DM/PM hospitalizations, malnutrition was associated with higher odds of major complications and greater healthcare resource utilization. These findings suggest that inpatient nutritional risk assessment may help inform risk stratification during hospitalization for DM/PM.</p> <p><Table Float="No" ID="Taba"> <tgroup cols="2"> <colspec align="left" colname="c1" colnum="1" /> <colspec align="left" colname="c2" colnum="2" /> <tbody> <row> <entry align="left" nameend="c2" namest="c1"> <p>Key Points</p> <p>• <i>In DM/PM hospitalizations, malnutrition occurred in 12.9% of admissions (NIS 2016–2022).</i></p> <p>• <i>In matched DM/PM analyses, malnutrition was associated with higher in-hospital mortality and major complications.</i></p> <p>• <i>Malnutrition was associated with greater resource utilization in DM/PM admissions.</i></p> </entry> </row> </tbody> </tgroup> </Table></p>