Background: Cardiomyopathy is universal in Duchenne muscular dystrophy (DMD). A previous study reported no correlation of body mass index (BMI) with cardiomyopathy1. Obesity (OB) is a well-established risk for cardiovascular disease (CVD). A recent large study reported that underweight (UW, BMI < 18.5 kg/m) was the strongest risk factor for CVD2. We sought to determine the impact of BMI on non-ambulatory DMD patients on the prevalence of late gadolinium enhancement (LGE) and cardiomyopathy by Cardiac MRI (CMR). Method: A retrospective review of CMRs of DMD patients≥ 15 years with LGE and LVEF data. Patients were divided into underweight (UW, BMI <18.5 kg/m), normal (NW, BMI ≥ 18.5 < 24.9 kg/m), overweight (OW, BMI ≥ 25 < 30 kg/m), and obese (OB, BMI ≥ 30 kg/m). The prevalence of LGE and LVEF was compared between groups. Results: 273 DMD patients who met the inclusion criteria are detailed in Table 1. There is no difference in age with expect difference in weight and BMI between groups. LV dilation is uncommon, but LGE is prevalent in all groups (UW=87.8%, NW=79.8%, OW=94.7% and OB=79.4%). LVEF is lowest in UW compared to both NW and OW group (49.8±11.5 vs 53.8±9.5 vs 54.8±10.3%, p =0.02 and 0.006, respectively) with no difference compared to OB group (52.4±11.9%, p = 0.15). Conclusion: UW is associated with lower LVEF and more cardiomyopathy compared to NW or OW patients. This study highlights the importance of lower BMI as a potential sign of advanced disease. Future longitudinal study is needed to better understand how BMI affects cardiomyopathy. References: 1. McKane M, Soslow JH, Xu M, et al. Does Body Mass Index Predict Premature Cardiomyopathy Onset for Duchenne Muscular Dystrophy? J Child Neurol. 2017;32(5):499-504. 2. Park D, Lee JH, Han S. Underweight: another risk factor for cardiovascular disease?: A cross-sectional 2013 Behavioral Risk Factor Surveillance System (BRFSS) study of 491,773 individuals in the USA. Medicine (Baltimore). 2017;96(48):e8769.