A 28-year-old man presents with facial swelling, swelling of both legs, and frothy urine for five days. The facial swelling was most prominent around the eyes, being worst at morning and slowly resolving throughout the day. There is no history of fever, dysuria, urgency, or hematuria. His urine output is normal. No other symptoms are present.

His medical and surgical histories are unremarkable. In particular, there is no history of obstructive sleep apnea. He is not on any medications, including herbal supplements or over-the-counter drugs. He does not have a history of chemical exposure, radiation, or infection. He has never smoked, only drinks socially, and denies using recreational drugs. His family history is unremarkable.

A complete blood count, renal profile, liver profile, random plasma glucose, HbA1c, lipid profile, and urinalysis are performed. These are only significant for a serum albumin of 1.9 g/dL (3.5-5.5), triglycerides of 450 mg/dL (<150), 3+ proteinuria, hyaline casts on urine microscopy, and a urinary protein:creatinine ratio of 3.2 mg/mg (<0.11).