Primary membranous nephropathy with isolated proteinuria

This code signifies a kidney disorder characterized by immune complex deposition in the glomerular basement membrane, leading to proteinuria without the full constellation of symptoms defining nephrotic syndrome. It represents a specific form of primary glomerulonephritis where the primary manifestation is protein leakage into the urine.

Apply this code when documentation explicitly states primary membranous nephropathy and specifies "isolated proteinuria" or "non-nephrotic range proteinuria." This diagnosis is typically confirmed by renal biopsy findings consistent with membranous nephropathy, and laboratory results showing proteinuria without significant hypoalbuminemia, edema, or hyperlipidemia.

• Ensure documentation clearly differentiates isolated proteinuria from nephrotic syndrome; the presence of edema, hypoalbuminemia, and hyperlipidemia would point to N04.21.
• Confirm that the membranous nephropathy is explicitly stated as "primary" to avoid confusion with secondary forms.
• Do not code this alongside N04.21, as per the Excludes1 note.