Reversibly reduced lipoprotein lipase in APOA5 c.553G>T-related hypertriglyceridemia successfully treated with pemafibrate

Summary: We report the case of a 47-year-old woman with severe hypertriglyceridemia due to a homozygous APOA5 c.553G>T (p.Gly185Cys) mutation. She presented with markedly elevated triglyceride levels (TG, 1,047 mg/dL) that were unresponsive to lifestyle modifications. Lipoprotein fractionation revealed increased chylomicrons (CMs, 21%) and very-low-density lipoprotein (35%), consistent with type V hyperlipoproteinemia. Secondary causes, such as diabetes, alcohol intake, and hypothyroidism, were excluded. The post-heparinization lipoprotein lipase (PH-LPL) level was reduced (104 ng/mL), indicating impaired lipolysis. Genetic testing revealed no pathogenic variants in LPL or other major genes related to triglyceride metabolism. A homozygous APOA5 c.553G>T variant was identified. Pemafibrate (0.2 mg/day), a selective PPARα modulator (SPPARMα), was initiated. After 2 months, the blood lipid levels had markedly improved, with the complete disappearance of CMs, and the PH-LPL level had normalized to 173 ng/mL. This case highlights the potential pathogenic role of APOA5 mutations in LPL-related hypertriglyceridemia. Furthermore, it demonstrates the multifaceted therapeutic effects of pemafibrate, suggesting a potential role for SPPARMα therapy in the management of hereditary hypertriglyceridemia. Learning points: Homozygous APOA5 mutations can cause reduced LPL protein levels, leading to severe hypertriglyceridemia with elevated CMs and VLDL. Pemafibrate may improve both LPL levels and lipid profiles, even in cases with reduced LPL protein and chylomicronemia. ApoA5-related chylomicronemia can resemble familial chylomicronemia syndrome but may respond to therapies such as pemafibrate, highlighting the importance of accurate genetic diagnosis.