N04.21
BillablePrimary membranous nephropathy with nephrotic syndrome
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is N04.21 an HCC code?
No. N04.21 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
N04.21 is the ICD-10-CM diagnosis code for primary membranous nephropathy with nephrotic syndrome. A kidney disorder where the kidney's filtering membrane thickens without an identifiable underlying disease, causing significant protein loss in the urine. N04.21 sits in the ICD-10-CM chapter for diseases of the genitourinary system (n00-n99), within the section covering glomerular diseases (n00-n08).
N04.21 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Primary membranous nephropathy is idiopathic; ensure documentation confirms no secondary cause is present.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for N04.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Primary membranous nephropathy is idiopathic; ensure documentation confirms no secondary cause is present
- •This is the most common form of membranous nephropathy in adults; verify the diagnosis is confirmed by kidney biopsy when possible