Focal segmental glomerulosclerosis with heterozygous apolipoprotein E5 (Glu3Lys)

Apolipoprotein (apo) E5 is a rare apoE isoform. The apoE5 (Glu3Lys) variant, which is caused by the substitution of lysine with glutamic acid at codon 3, has a relative frequency of 0.1% in Japan. Previous studies have reported that apoE5 (Glu3Lys) is associated with hyperlipidemia and cardiovascular diseases, but this isoform has higher LDL receptor-binding activity than that of normal apoE3. Nephropathy associated with apoE5 (Glu3Lys) alone has not yet been reported. We present a case of a 51-year-old man with nephrotic syndrome. On renal biopsy, three glomeruli showed segmental sclerosis with hypertrophy of podocytes and intracapillary marked infiltration of intraglomerular foam cells. These findings were compatible with focal segmental glomerulosclerosis (FSGS). The patient had mild diabetes mellitus and monoclonal gammopathy of undetermined significance, but there were no specific findings of nephrolopathy related to these diseases. Various factors are involved in the pathogenesis of FSGS, including dyslipidemia and apoE activity. Our findings suggest that abnormal lipid metabolism by ApoE5 (Glu3Lys) is involved in the onset of FSGS.