This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
Proteinuria caused by tubule-interstitial renal disease is confirmed by excretion of - 
Select and explain. 
A. Albumin, B. Light chain, C. Immunoglobulin A, D. Tamm-Horsfall protein
B: Light chain
Answer: B: Light chain 
Explanation: Tubular proteinuria is a result of tubulointersitial disease affecting the proximal renal tubules and interstitium. This results in decreased proximal reabsorption of proteins--in paicular, low molecular weight proteins (generally below 25,000 Daltons) such as beta-2 microglobulin (light chain) are excreted Ref Harrison20th edition pg 295