A rare case of familial chylomicronemia in infancy due to homozygous LMF1 variant.

Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive disorder of triglyceride (TG) metabolism, with an estimated prevalence of 1 in 100 000 to 1 in 1 000 000. It typically presents in childhood or adolescence, while presentation in infancy is exceedingly rare. Loss-of-function variants in lipoprotein lipase gene account for 60-80% of FCS cases. Other causes of FCS include loss-of-function variants in glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1, apolipoprotein A-V, apolipoprotein C-II, and lipase maturation factor 1 (LMF1) genes. LMF1 variants are an exceedingly rare cause of FCS. We report a rare case of FCS presenting in a 5-month-old infant due to a homozygous variant in the LMF1 gene, detected incidentally. Early diagnosis and timely dietary intervention resulted in significant improvement in serum TG levels and prevented complications like pancreatitis. This case highlights a rare presentation of FCS due to a homozygous LMF1 variant presenting in infancy.