Adult-Onset Focal Segmental Glomerulosclerosis With Steroid-Dependent Nephrotic Syndrome Caused by a Novel TBC1D8B Variant: A Case Report and Literature Review.

Focal and segmental glomerulosclerosis (FSGS) is a histological lesion due to many causes including rare mutations of podocyte related genes. Recently, it has been found that TBC1D8B mutations can lead to early-onset FSGS and steroid-resistant nephrotic syndrome (NS) by influencing endocytic and recycling of nephrin. Here, we report a 19-year-old Chinese patient with NS and normal renal function. He had a complete remission of NS after full-dose prednisone and cyclosporine treatment. Unfortunately, a relapse of NS occurred during prednisone tapering. FSGS was proven by a renal biopsy and a hemizygous pathogenic mutation located in TBC domain of TBC1D8B was detected by whole exome sequencing (WES). By a literature review, we summarized the genotype-phenotype correlation among all the probands with TBC1D8B mutations. To our knowledge, this is the first report identifying a pathogenetic mutation located in TBC domain of TBC1D8B in an adult-onset FSGS patient with steroid dependent NS. With this report, we broaden the clinical and genetic spectrum of X-linked genetic FSGS.