A case report of youth-onset lipoprotein glomerulopathy with APOE Chicago mutation

This article reports an extremely rare case of lipoprotein glomerulopathy (LPG) with apolipoprotein E gene (APOE) Chicago mutation in a young Chinese male. Only five cases or families with APOE Chicago mutations have been reported in the literature.

The young male patient is manifested with nephrotic syndrome, accompanied by hyperlipidemia with a preferable increase in triglycerides and elevated ApoE level. Renal biopsy of the patient showed highly dilated glomerular capillaries filled with vacuolar lipids, segmentally fused podocyte foot processes, vacuolar degeneration of renal tubular epithelial cells and absence of electron-dense material, which indicates the diagnosis of LPG. Whole-exome gene sequencing identified the heterozygous mutation of NM_000041.4:c.494G > C (p.Arg165Pro), which is in the exon 4 of the APOE gene and also known as APOE Chicago mutation, a rare mutation of LPG. Further family pedigree gene analysis clarified that the mutation was inherited from the patient's mother, who does not have high ApoE levels or renal manifestations. This is also consistent with the incomplete penetrance of APOE gene mutations in LPG. Under lipid-lowering treatments, including a low-fat diet and fenofibrate, the patient's urinary protein was partially controlled, and the albumin level was recovered.

Patients with nephrotic syndrome and elevated ApoE levels should be prompted into renal biopsy to avoid delay of appropriate treatment and unnecessary use of glucocorticoids. This case of LPG was diagnosed by renal biopsy and further verified with genetic sequencing. The timely diagnosis and treatment improved the patient's symptoms. This case is one of only six reported LPG cases or families with APOE Chicago mutation in the world.