Synopsis
Interpret an MPGN biopsy pattern mechanistically, identify immune-complex and complement drivers, and route rare C3 disease to specialist care.
- MPGN is a light-microscopic pattern of mesangial proliferation and capillary-wall remodelling, not a single aetiological diagnosis.
- Immunofluorescence separates immunoglobulin-associated immune-complex disease from C3-dominant glomerulopathy and directs the subsequent search.
- Immune-complex MPGN prompts evaluation for chronic infection, autoimmunity, cryoglobulinaemia and monoclonal gammopathy; genuinely idiopathic disease is uncommon.
- C3 glomerulopathy reflects alternative-complement-pathway dysregulation and comprises C3 glomerulonephritis and dense deposit disease, distinguished mainly by electron microscopy.
- Low serum C3 can support complement activation but may be normal, while reduced complement also occurs in immune-complex disease and is not diagnostic alone.
- Complement autoantibody, functional and genetic testing belongs in specialist laboratories and should follow careful phenotyping and exclusion of secondary drivers.
- Proteinuria control, blood-pressure management and cardiovascular protection remain important while disease-specific treatment is considered.
- New complement-directed therapies and their NHS status are evolving; use only current NICE, NHS England and expert-centre governance, never a historical web page as a prescription.
Key red flags
Oliguria, accelerating creatinine, severe hypertension or fluid overload may reflect active proliferative injury and requires urgent nephrology assessment.
Fever, cardiac murmur, injected-drug exposure, indwelling infection or hepatitis risk should redirect evaluation before immunosuppression is contemplated.
Investigation priorities
Define the MPGN pattern, dominant deposits, ultrastructure and chronic damage.
Management branches
Renal histology is reported as membranoproliferative or mesangiocapillary.
- Review immunofluorescence dominance and electron-microscopy deposit location with an experienced renal pathologist.
- Map immunoglobulin-associated lesions to infection, autoimmune, cryoglobulin and monoclonal-protein pathways; map C3-dominant lesions to complement assessment.
- Reconcile histology with serology and clinical course, seeking a second pathology opinion when classification will determine high-risk treatment.
Key medicines
ACE inhibitor or angiotensin-receptor blockerBegin and titrate one class according to the current CKD formulary, blood pressure, proteinuria, potassium and eGFR, with early laboratory review.Avoid dual blockade. Reassess during dehydration, sepsis, hypotension, hyperkalaemia or a large creatinine rise; pregnancy and renal-artery stenosis precautions still apply.
Disease-specific immune or complement therapyNo universal regimen is safe for an MPGN pattern. A specialist centre must select any immunosuppressive, clone-directed or complement inhibitor using the live indication, NICE decision, commissioning policy and SmPC.Exclude infection first; assess vaccination, encapsulated-organism prophylaxis where relevant, blood counts, immunoglobulins, fertility and organ-specific toxicity. Historical evidence or a trial protocol is not authority to prescribe.