A 72-year-old obese man presents for a routine check-up. He had basic lab work prior to this visit, which included

a comprehensive metabolic panel, glycosylated hemoglobin, and urinalysis. The patient is generally well but has not been sleeping well. The patient feels like he wakes every few hours to urinate. He also feels tired “all of the time,” attributing this to the lack of a good night’s sleep. The patient’s only known history is elevated cholesterol, but he has not visited a doctor in many years and only presents today at his wife’ request.

Labs are as follows: WBC 8.9, HgB 14, HCT 35, Plt 230, Na 137, K 4.1, Cl 91, CO3 27, BUN 27, Cr 1.9, A1C 13.2, AST 21, ALT 17, Alb 4.1, UA: leuk, Esterase: neg, Blood: neg, WBC 0-2, RBC 0-5, and Protein >500. What is the cause of his proteinuria?