Low Molecular Weight Proteinuria in Children with Distal Renal Tubular Acidosis

Distal renal tubular acidosis (dRTA) (MIM #267300, #602722 and #179800) is a rare inherited tubulopathy characterized by the inability of the distal tubule to acidify the urine with consecutive systemic acidosis. The clinical features include polyuria, polydipsia, poor appetite, failure to thrive, short stature and rickets. Prominent biochemical features are hypokalemia, hypercalciuria and hypocitraturia. There are reports on patients who presented with unusual biochemical features such as low molecular proteinuria, hypophosphatemia, hypouricemia, generalized hyperaminioaciduria, hyperoxaluria and other making diagnostic confusion to the clinicians. In this work, we report on a series of 8 children with clinically, biochemically and genetically proven dRTA who present with low molecular proteinuria at the disease onset. With metabolic compensation of the disease, there was complete resolution of the low molecular weight protenuria and other proximal tubular abnormalities in all children. Late recognition of the disease with long standing hypokalemia and acidosis may result in abnormal expression and function of the transporters in the proximal tubules. Sodium dodecyl sulphate polyacrylamide gel electrophoeresis is an accurate method for detection and follow up of patients with low molecular weight proteinuria.