Origin of Proteinuria as Observed from Qualitative and Quantitative Analysis of Serum and Urinary Proteins

It is well known that proteins present in the primary urine are reabsorbed in the renal proximal tubules, and that this reabsorption is mediated via the megalincubilin complex and the neonatal Fcgamma receptor. However, the reabsorption is also thought to be influenced by an electrostatic interaction between protein molecules and the microvilli of the renal proximal tubules. By analyzing the charge diversity of urinary IgG, we showed that this reabsorption process occurs in a cationic charge-preferential manner. The charge-selective molecular sieving function of the glomerular capillary walls has long been a target of research since Brenner et al. demonstrated the existence of this function by a differential clearance study by using the anionic dextran sulfate polymer. However, conclusive evidence was not obtained when the study was performed using differential clearance of serum proteins. We noted that immunoglobulin (Ig) A and IgG have similar molecular sizes but distinct molecular isoelectric points. Therefore, we studied the differential clearance of these serum proteins (clearance IgA/ clearance IgG) in podocyte diseases and glomerulonephritis. In addition, we studied this differential clearance in patients with Dent disease rather than in normal subjects because the glomerular sieving function is considered to be normal in subjects with Dent disease. Our results clearly showed that the charge-selective barrier is operational in Dent disease, impaired in podocyte disease, and lacking in glomerulonephritis.

A 3-year-old girl with Wernicke’s encephalopathy due to a severely unbalanced diet

Wernicke’s encephalopathy, an acute neuropsychiatric syndrome caused by thiamine (vitamin B1 ) deficiency, is associated with serious clinical disease and can be fatal. It has rarely been reported in infants and children. We report a case of a 3-year-old girl with Wernicke’s encephalopathy. The patient’s diet had been severely unbalanced since the age of 2 years, and for about a month prior to admission to our hospital had consisted almost exclusively of polished white rice and noodles. Her clinical symptoms supported thiamine deficiency-related neuropathy. Brain MRI findings revealed abnormalities consistent with pediatric Wernicke’s encephalopathy with involvement of the putamen. The diagnosis prompted thiamine replacement therapy, to which the patient showed an excellent response.