Most common cause of nephrotic range proteinuria in an adult is:
Focal Segmental Glomerulosclerosis (FSGS) is the most common cause of nephrotic syndrome in adults. Diabetes mellitus, Amyloidosis, SLE and Sjogren's syndrome are secondary causes of nephrotic syndrome. Since diabetes mellitus is more prevalent than amyloidosis and other diseases, diabetes mellitus is the best choice amongst the options provided. Ref: Harrison's Internal Medicine 1st Edition, Page 1684; Davidson's principles and practice of Medicine, 20th Edition, Chapter 17, Page 479, 480 & 499.
Diabetes mellitus
Amyloidosis
Hypeensive nephropathy
Wegner's Granulomatosis