Dear Editor,
Regarding recently published article on urinary beta-2 microglobulin (ß2MG) as a prognostic marker in children with pyelonephritis, some issues should be considered (1). ß2MG is a small globular peptide with a molecular weight of 11800 Dalton which can be found on the surface of many cells. It consists of 100 amino acids with a disulfide-linked loop between amino acid 25 and 81; and its tertiary structure is homologous to the CH3- IgG domain. ß2MG passes freely through the glomerular membrane. Thereafter it is reabsorbed to an amount of maximum 99.9% by the proximal tubules (2). In aforementioned interesting article, the relation between urinary ß2M to Creatinine ratio and its effect on kidney damage may not be an incidental finding. Although it is possible to apply ß2M as a prognostic factor in patients with pyelonephritis, but exclusion criteria for patients should be extended more than mentioned. Other contributing factors in increased ß2M are infections (such as CMV and HIV), malignancies (i.e. multiple myeloma), exposure to heavy metals (Mercury, Cadmium), kidney transplant, amyloidosis and drugs (such as Lithium, Cyclosporine, Cisplatin, Aminoglycosides). These issues should be taken into account and are considered in the exclusion criteria (3-6).