In an adult with nephrotic‑range proteinuria and biopsy‑proven membranous nephropathy, what does a negative anti‑phospholipase A2 receptor (anti‑PLA2R) antibody result indicate and how should I manage it?

False Negative Anti-PLA2R Antibody in Membranous Nephropathy

A negative anti-PLA2R antibody test in biopsy-proven membranous nephropathy requires immediate evaluation for secondary causes (malignancy, lupus, hepatitis B/C, medications) and mandates kidney biopsy tissue staining for PLA2R antigen to distinguish between immunologic remission and true seronegative disease. 1

Understanding Seronegative Membranous Nephropathy

Anti-PLA2R antibodies are detected in only 70–80% of primary membranous nephropathy cases, meaning 20–30% of patients with genuine primary disease will test negative. 1, 2 Seronegative patients fall into two distinct categories that require different management approaches:

Category 1: Recent Immunologic Remission

• Patients may be seronegative because they have recently entered spontaneous remission, with circulating antibodies already cleared from serum. 1
• These patients may still have PLA2R antigen detectable in glomerular immune deposits on kidney biopsy tissue immunofluorescence staining, confirming primary disease despite negative serology. 3, 1
• This scenario represents true primary membranous nephropathy with favorable prognosis. 1

Category 2: True Seronegative Disease

• Patients lacking both circulating anti-PLA2R antibodies and tissue PLA2R antigen have either secondary membranous nephropathy or primary disease driven by alternative antigens (THSD7A, NELL1, or yet-unidentified targets). 1, 4
• Secondary causes are significantly more likely in this group and must be systematically excluded. 1, 4

Mandatory Evaluation for Secondary Causes

All anti-PLA2R negative patients require comprehensive screening regardless of clinical presentation: 1, 2

• Malignancy screening: Age-appropriate cancer tests including colonoscopy, mammography, PSA, and chest imaging; consider contrast-enhanced CT chest/abdomen/pelvis in patients >60 years or with constitutional symptoms. 1, 5
• Autoimmune evaluation: ANA, anti-dsDNA, complement levels (C3, C4) to exclude systemic lupus erythematosus. 1, 2
• Infectious workup: Hepatitis B surface antigen, hepatitis C antibody, HIV testing. 1, 2
• Medication review: NSAIDs, gold, penicillamine, anti-TNF agents. 1, 2

The association between malignancy and membranous nephropathy is more frequent in older patients and may be causal or coincidental, but systematic screening is essential. 1

Critical Role of Kidney Biopsy Tissue Analysis

Kidney biopsy tissue immunofluorescence staining for PLA2R antigen provides critical diagnostic information that serology cannot: 3, 4

• Strong glomerular PLA2R staining on tissue correlates tightly with serum antibodies and confirms primary disease even when serology is negative due to recent remission. 4
• Faint or absent PLA2R staining in glomeruli, combined with negative serology, strongly suggests secondary membranous nephropathy or alternative antigen-driven disease. 4
• Enhanced PLA2R expression in glomeruli was found in 61 of 88 patients, with 60 of these having positive serum antibodies; the 27 seronegative patients showed only faint glomerular staining, and 15 had identifiable secondary causes. 4

The degree of chronic interstitial fibrosis and tubular atrophy on biopsy is a major adverse prognostic factor that guides whether to pursue conservative or aggressive therapy. 3

Management Algorithm for Seronegative Patients

Step 1: Confirm True Seronegativity

• Weakly positive results require confirmation with additional assays or repeat testing to exclude false negatives. 3, 1
• Consider immunofluorescence-based antibody testing if ELISA was initially used, as immunofluorescence is more sensitive. 3

Step 2: Tissue PLA2R Staining

• Request immunofluorescence staining of biopsy tissue for PLA2R antigen if not already performed. 3, 1
• Strong tissue positivity with serum negativity indicates recent immunologic remission—these patients have primary disease with excellent prognosis. 1, 4
• Absent or faint tissue staining mandates aggressive secondary cause evaluation. 4

Step 3: Risk Stratification for Treatment

Do not initiate immunosuppression if all of the following are present: 1, 2

• Proteinuria <3.5 g/day
• Serum albumin >30 g/L
• eGFR >60 mL/min/1.73 m²

Consider immunosuppression when any of these apply: 1

• Persistent nephrotic syndrome (proteinuria ≥4 g/day, ≥50% of baseline, unchanged after 6 months of optimal RAAS blockade)
• Severe nephrotic complications (acute kidney injury, infections, thromboembolism)
• Declining kidney function (≥30% rise in creatinine over 6–12 months with eGFR still >25–30 mL/min/1.73 m²)

Contraindications to immunosuppression: 1

• Serum creatinine persistently ≥3.5 mg/dL (eGFR ≤30 mL/min/1.73 m²)
• Kidney size <8 cm on ultrasound

Step 4: Serial Monitoring Strategy

• Repeat anti-PLA2R antibody testing every 3–6 months even if initially negative, as seroconversion can occur and predicts disease progression. 1, 6
• Rising antibody titers forecast disease relapse before proteinuria increases, allowing preemptive therapeutic adjustments. 1, 6
• Monitor proteinuria, serum albumin, and eGFR every 3 months during observation period. 1

First-Line Immunosuppressive Options (When Indicated)

When treatment criteria are met, choose among: 1

• Rituximab (preferred in many centers due to favorable safety profile)
• Cyclophosphamide with alternating monthly glucocorticoids for 6 months
• Tacrolimus-based therapy for ≥6 months

Critical Pitfalls to Avoid

• Do not assume negative PLA2R serology excludes primary disease—tissue staining may reveal recent immunologic remission. 3, 1
• Do not skip secondary cause evaluation—even positive PLA2R antibodies do not exclude concurrent malignancy, lupus, or hepatitis. 1, 5, 2
• Do not use THSD7A or NELL1 antibodies alone for diagnosis—these lack the diagnostic accuracy of PLA2R testing and require biopsy confirmation. 3, 2
• Do not delay biopsy when eGFR is rapidly declining—this suggests alternative or additional pathology requiring histologic evaluation. 3, 2
• Do not base treatment decisions on single antibody measurements—serial trends provide far more reliable guidance than isolated values. 1, 2
• Do not ignore mesangial deposits on electron microscopy—these occur in 27.5% of PLA2R-positive cases and do not reliably distinguish primary from secondary disease. 7