Condition Deep-Dives 11 min read·Updated 22 July 2026 Clinician-reviewed

Fibrillary Glomerulonephritis

A UK Consultant Nephrologist on fibrillary glomerulonephritis — a rare but increasingly recognised cause of proteinuric CKD now defined by DNAJB9 staining. Despite no licensed treatment, modern care with RAS-blockade, SGLT2 inhibition and rituximab is meaningfully changing outcomes.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 22 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

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Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

FGN: rare (~0.5–1% of biopsies). Congo-red NEGATIVE randomly arranged 10–30 nm fibrils + DNAJB9 staining. Presents with proteinuria, haematuria, CKD. Screen for HCV, paraprotein, autoimmunity and malignancy. RAS-blockade + SGLT2; rituximab for progressive disease. ~50% reach ESKD by 4 years; transplant is reasonable.

Key recommendation: DNAJB9 stain is the diagnostic gold standard.

Quick answer

✓ Best choices

  • Plant proteins: beans, lentils, tofu, tempeh, chickpeas
  • Vegetables, fruit and whole grains
  • Oily fish 1–2 times a week
  • Olive oil as the main cooking fat

✓ Foods to limit

  • Added salt (≤ 6 g/day)
  • Processed meats and high-additive ready meals
  • Excess animal protein at every meal

Key takeaway

FGN: rare (~0.5–1% of biopsies). Congo-red NEGATIVE randomly arranged 10–30 nm fibrils + DNAJB9 staining. Presents with proteinuria, haematuria, CKD. Screen for HCV, paraprotein, autoimmunity and malignancy. RAS-blockade + SGLT2; rituximab for progressive disease. ~50% reach ESKD by 4 years; transplant is reasonable.

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Fibrillary Glomerulonephritis

Epidemiology & presentation

Epidemiology

  • 0.5–1% of native kidney biopsies
  • Median age 55–65; M:F ~ 1:1; predominantly white patients in reported series

Presentation

  • Proteinuria — nephrotic in ~ 40%
  • Microscopic haematuria in ~ 60%
  • Hypertension in ~ 70%
  • Reduced eGFR at diagnosis (median ~ 45 mL/min/1.73 m²)
  • Slow but progressive decline; ~ 50% ESKD at 4 years

ASSOCIATIONS (screen all patients):

  • Hepatitis C
  • Autoimmune disease: Sjögren, SLE, rheumatoid arthritis, Crohn's
  • Monoclonal gammopathy (~ 15–20%); may meet MGRS criteria
  • Solid-organ malignancy (~ 20%) and lymphoproliferative disease
  • Diabetes

Diagnosis

BIOPSY (essential):

  • Light microscopy: mesangial expansion, mesangiocapillary or membranoproliferative pattern, occasional crescents
  • Congo-red NEGATIVE (vs amyloid positive)
  • Immunofluorescence: smudgy mesangial and capillary wall IgG (often IgG4-dominant), C3, with kappa AND lambda light chains (vs monoclonal in amyloid / MIDD / immunotactoid)
  • Electron microscopy: randomly arranged Congo-red-negative fibrils 10–30 nm diameter (vs 8–12 nm in amyloid, 30–50 nm parallel microtubules in immunotactoid)
  • DNAJB9 immunostain: positive in > 98% of FGN; rapidly becoming the diagnostic gold standard

Screening In Every Patient

  • Hepatitis C antibody and PCR
  • Hepatitis B serology, HIV
  • Serum and urine electrophoresis with immunofixation and serum free light chains (assess for MGRS)
  • ANA, complement, anti-Ro/La, RF, anti-CCP
  • Age-appropriate cancer screening (mammography, colonoscopy, CT chest/abdomen/pelvis if clinical suspicion)
  • If monoclonal protein: bone marrow biopsy ± PET-CT

Differential

  • Renal amyloidosis (Congo-red +, 8–12 nm fibrils)
  • Immunotactoid glomerulopathy (larger 30–50 nm tubules, strong monoclonal association)
  • Membranoproliferative GN
  • Cryoglobulinaemic GN

Management & outcomes

General CKD Measures

  • ACE inhibitor or ARB to maximum tolerated dose
  • SGLT2 inhibitor (dapagliflozin / empagliflozin) for proteinuria + CKD per DAPA-CKD / EMPA-KIDNEY
  • BP target < 130/80
  • Statins
  • Low-sodium, plant-forward diet
  • Anticoagulation prophylaxis if nephrotic and albumin < 20 g/L

Treat Associated Conditions

  • Hepatitis C — direct-acting antivirals (sofosbuvir/velpatasvir) often improve proteinuria
  • Monoclonal gammopathy — treat as MGRS with clone-directed therapy (bortezomib-based regimens)
  • Active malignancy — treat per oncology
  • Autoimmune disease — disease-specific

IMMUNOSUPPRESSION (no licensed regimen):

  • RITUXIMAB — 1 g × 2 doses (2 weeks apart) or 375 mg/m² × 4 weekly doses
  • Most evidence; stabilises eGFR in ~ 40–50%; may need repeated cycles
  • Reserve cyclophosphamide / steroids for crescentic or rapidly progressive disease
  • Calcineurin inhibitors and MMF have minimal evidence
  • Consider transplant referral when eGFR < 20 with progression

Transplant

  • FGN can recur in the graft (~ 30%) but graft loss from recurrence is uncommon (~ 6%)
  • Transplant is appropriate for most patients
  • Living donation suitable; no specific donor restriction

Follow-up

  • Every 1–3 months while active
  • ACR, eGFR, BP, weight, paraprotein every 6 months
  • Repeat malignancy screening at intervals appropriate to age and findings
Membranous Nephropathy
Related reading: Membranous Nephropathy.

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • Take prescribed ACE inhibitor / ARB / SGLT2 inhibitor consistently — diet works alongside, not instead
  • Monitor BP at home weekly
  • Review urine ACR with your team to track progress

Clinical guidance

TL;DR summary

FGN: rare (~0.5–1% of biopsies). Congo-red NEGATIVE randomly arranged 10–30 nm fibrils + DNAJB9 staining. Presents with proteinuria, haematuria, CKD. Screen for HCV, paraprotein, autoimmunity and malignancy. RAS-blockade + SGLT2; rituximab for progressive disease. ~50% reach ESKD by 4 years; transplant is reasonable.

Key takeaways
  • DNAJB9 stain is the diagnostic gold standard.
  • Congo-red negative (vs amyloid).
  • Always screen for HCV, paraprotein, cancer, autoimmunity.
  • Rituximab is the most widely used immunotherapy.
  • Graft recurrence is uncommon; transplant is appropriate.
Kidney Diet & Nutrition Considerations

When protein is leaking into the urine, the goal is to protect the remaining kidney function. Dietary protein should be sensible — neither very high nor unnecessarily low — and a Mediterranean-style plate with reduced salt supports both blood pressure and albuminuria reduction alongside ACE inhibitors, ARBs or SGLT2 inhibitors.

Foods to prioritise

  • Plant proteins: beans, lentils, tofu, tempeh, chickpeas
  • Vegetables, fruit and whole grains
  • Oily fish 1–2 times a week
  • Olive oil as the main cooking fat

Foods to limit

  • Added salt (≤ 6 g/day)
  • Processed meats and high-additive ready meals
  • Excess animal protein at every meal

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

What is fibrillary glomerulonephritis?

Fibrillary glomerulonephritis (FGN) is a rare glomerular disease (≈ 0.5–1% of native biopsies) defined by Congo-red-negative randomly arranged fibrils 10–30 nm in diameter on electron microscopy. The key modern diagnostic marker is DNAJB9, a heat-shock protein that is present in > 98% of FGN cases and gives a strong glomerular immunostain — discovered in 2017, it has transformed diagnosis.

How do patients present?

Most patients are middle-aged adults presenting with proteinuria (often nephrotic-range), microscopic haematuria, hypertension and reduced eGFR. About 40% are nephrotic at diagnosis. Up to a third have an associated condition — hepatitis C, autoimmune disease (Sjögren, SLE, rheumatoid), monoclonal gammopathy or solid-organ cancer — and these should always be screened for.

How is it treated?

There is no standard regimen. Optimise RAS-blockade, blood pressure, lipids and SGLT2 inhibition. For progressive disease, rituximab (1 g × 2 doses) is the most widely used immunosuppressive treatment and stabilises eGFR in roughly half of patients. Cyclophosphamide and steroids have been used historically. Treat any associated condition (HCV, monoclonal gammopathy). Half of patients still reach ESKD within 4 years — but recurrence in the transplant is uncommon enough that transplantation remains an appropriate option.

How is FGN different from immunotactoid glomerulopathy and amyloid?

All three diseases show organised deposits. Amyloid is Congo-red positive with 8–12 nm fibrils. FGN has 10–30 nm randomly arranged Congo-red-negative fibrils that are DNAJB9 positive. Immunotactoid glomerulopathy has larger 30–50 nm microtubules in parallel arrays and a much stronger association with monoclonal gammopathy and lymphoproliferative disease. The distinction matters for prognosis and treatment.

Can diet reduce protein in urine?

A reduced-salt, Mediterranean-style diet with sensible protein intake can lower urine protein, particularly when combined with prescribed ACE inhibitors, ARBs or SGLT2 inhibitors. Very low-protein diets are not routinely recommended without dietitian supervision.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Built around UK guidance

Aligned with KDIGO 2021 glomerular disease guidance, UK Kidney Association GN guidance, NHS National Amyloidosis / Renal Pathology services, and modern DNAJB9 nomenclature.

Designed by a UK Consultant Nephrologist

Formulated and reviewed by Professor Mohammed Mahdi Althaf (GMC 7216325).

Screen-everything approach

Practical UK guidance to systematically rule out HCV, paraprotein, autoimmunity and malignancy before committing to immunosuppression.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). Nephrologist Developed Daily Multivitamin.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • No Added Iron
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

View Full Biography

Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

View professional profile →
View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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