Familial Chylomicronemia Syndrome With a Novel Homozygous LPL Mutation Identified in Three Siblings in Their 50s

Familial chylomicronemia syndrome: The first case reported in Ecuador

Familial chylomicronemia syndrome (FCS) is a genetic entity with autosomal recessive inheritance. Mutations in genes (such as APOC2, APOAV, LMF-1, GPIHBP-1) that code for proteins that regulate the maturation, transport, or polymerization of lipoprotein lipase-1 are the most common causes, but not the only ones. The objective of this study was to report the first documented case in Ecuador. CLINICAL CASE: A 38-year-old man presented with chronic hepatosplenomegaly, thrombocytopenia, pancreatic atrophy, and severe hypertriglyceridemia refractory to treatment. A molecular analysis was performed by next generation sequencing that determined a deficiency of Lipoprotein Lipase OMIM #238600 in homozygosis. Genetic confirmation is necessary in order to establish the etiology of HTGS for an adequate management of this pathology.

Novel pathogenic variant combination in LPL causing familial chylomicronemia syndrome in an Asian family and experimental validation in vitro: a case report

BACKGROUND

Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive disorder, typically caused by biallelic pathogenic variants in the lipoprotein lipase (LPL) gene. Lipoprotein lipase, encoded by the LPL gene, catalyzes the hydrolysis of triglycerides, and its deficiency or dysfunction can lead to chylomicronemia and potentially fatal recurrent acute pancreatitis.

CASE DESCRIPTION

Here, we report an Asian child with FCS due to compound heterozygous LPL variants. The 4-year-old patient presented with splenomegaly and severe hypertriglyceridemia, specifically chylomicronemia which resulted in abnormal coagulation measured by a turbidity-based assay. Based on the clinical features and family history, the diagnosis of FCS was suspected, and confirmed by the identification of compound heterozygous variants in the LPL gene (c.461A>G; p.His154Arg and c.788T>A; p.Leu263Gln) in the patient, inheriting one from each parent. According to the clinical and genetic findings, the patient was diagnosed with FCS. In vitro experimental validation found that the LPL p.H154R variant reduced the expression of lipoprotein lipase and decreased its lipolytic activity, while the LPL p.L263Q variant mainly impaired its lipolytic activity.

CONCLUSIONS

FCS was molecularly diagnosed using whole exome sequencing in the case presented. When interpreting abnormal coagulation profiles measured by turbidity-based assay, the possibility of lipemic blood (or chylomicronemia) should be considered and the presence of this phenomenon might indicate the diagnosis of FCS. In vitro experiments showed that the two LPL variants impaired lipoprotein lipase expression and/or function making them likely to be pathogenic.