Cystatin C as a Multifaceted Biomarker in Kidney Disease and Its Role in Defining "Shrunken Pore Syndrome"

Cystatin C, a basic nonglycosylated 13.3 kDa protein comprising a single polypeptide chain of 120 amino acid residues, is produced at a stable rate from a housekeeping gene in all nucleated cells and eliminated from the circulation by free filtration through the glomerular membranes as described in the first edition of "Biomarkers of Kidney Disease." This discourse will report some of the progress in the use of cystatin C as a multifaceted marker of kidney disease, which has occurred since then, including its role in identifying the novel syndrome called "Shrunken Pore Syndrome."