Abstract 4143142: Lost to Follow Up: A Rare Case of Malonyl-CoA Decarboxylase Deficiency Induced Cardiomyopathy in an Adult Spanish Speaking Hispanic Male

Introduction: Malonyl-CoA decarboxylase deficiency (MLYCDD) is a rare inherited metabolic disorder with multi-organ involvement, causing cognitive impairment, cardiomyopathy, seizures, hypotonia, and acidosis. Variants in MLYCCD, the gene for malonyl-CoA decarboxylase, disrupt long chain fatty acid synthesis in cardiac tissue. Prevalence is estimated to be less than 1 in 1,000,000, with cardiomyopathy being the leading cause of morbidity and mortality. Less than 40 cases have been documented, the majority of which detail newborns. No guidelines exist for treatment. A high-carbohydrate, low-fat diet, and levocarnitine reportedly improve cardiac function. Presentation: A 30-year-old Spanish-speaking male with MLYCDD, with resultant heart failure with reduced ejection fraction (EF) and cognitive delay, presented to a community hospital with malaise. He was diagnosed at age 9 and followed with an interdisciplinary team, receiving care in Spanish and English since diagnosis. His treatment consisted of levocarnitine and dietary restrictions that had led to cardiac recovery. At 24, his doctor retired, his insurance changed, and he was lost to follow-up, leading to dietary liberalization. On presentation, he was diagnosed with pneumonia complicated by atrial fibrillation (AF). AF was treated with a diltiazem infusion, resulting in cardiogenic shock with an EF of 15% from 39%. He was transferred to an academic center where diltiazem was stopped, inotropes started, and impella placed. He started enteral nutrition with liquid protein, dextrose infusion, medium-chain triglyceride (MCT) oil, and levocarnitine, along with supportive care for pneumonia. Given persistent shock he was transferred to our center for advanced therapies evaluation. Notable changes included replacing MCT oil with triheptanoin and stopping the dextrose infusion. A repeat echocardiogram showed recovery of EF to 40% Conclusions: MLYCDD exhibits a range of phenotypes, with limited data on long-term outcomes. This presentation is atypical: an adult with cardiomyopathy diagnosed in adolescence, successfully treated, who decompensated after stopping a modified diet in the setting of pneumonia and diltiazem. This case offers several clinical insights: (1) Restrictive diets with levocarnitine supplementation are instrumental in treating MLYCDD. (2) Avoid diltiazem in heart failure to prevent iatrogenic shock. (3) Language-concordant care ensures patients understanding and supports seamless care transitions.