Onset of Dierks's Disorder (IMAGE) Bielefeld University Caption The microscopic photo shows strong accumulations of heparan sulfate (blue-red coloring) in cells of the thick ascending limb (TAL) of renal tubules. The cause is ARSG enzyme deficiency. Credit Bielefeld University Usage Restrictions The image may only be used with appropriate caption or credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.