# Anti-GBM and Complement-Mediated Disease: Different Immune Routes

Pulmonary–renal anti-GBM disease is an emergency; complement-mediated disease requires a different diagnostic pathway.

![Infographic: Anti-GBM and Complement-Mediated Disease: Different Immune Routes](https://urinenephrology.org/visual-reference/images/student-complement-antigbm.png?v=20261003c)

## Recognize the anti-GBM emergency

Rapid creatinine rise with glomerular hematuria and possible hemoptysis/hypoxemia should prompt urgent nephrology evaluation. Pulmonary hemorrhage may occur even without striking hemoptysis.

## Send time-critical tests

Obtain anti-GBM antibodies, ANCA, urinalysis/protein quantification, blood count, creatinine, and appropriate chest assessment. Arrange kidney biopsy when feasible. Strong suspicion of organ-threatening disease warrants specialist treatment decisions before every result returns.

## The biopsy patterns differ

Anti-GBM disease classically produces linear IgG staining along the basement membrane. C3-dominant staining suggests a complement-mediated pattern; immune-complex deposits raise another differential. The staining pattern guides further testing.

## Understand anti-GBM treatment goals

Plasma exchange removes circulating antibody; immunosuppression reduces further production and inflammation. Kidney recovery potential, dialysis dependence, biopsy damage, and pulmonary hemorrhage affect decisions; no single creatinine cutoff substitutes for specialist assessment.

## Investigate a complement pattern

C3/C4 levels, infection assessment, monoclonal protein studies, and specialist complement testing help distinguish triggers and mechanisms. A low C3 alone does not prove C3 glomerulopathy or select a complement inhibitor.

## Worked distinction

Hematuria and AKI with pulmonary hemorrhage needs an urgent anti-GBM/ANCA pathway. Isolated low C3 with persistent proteinuria needs a pathology-led cause search. These presentations should not share one generic immunosuppression algorithm.

## Supporting evidence

- [KDIGO glomerular disease guideline suite: anti-GBM and complement disease](https://kdigo.org/guidelines/gd/)

## Source lessons

- [vasculitis complement student handout](https://urinenephrology.org/student-resources/glomerular/vasculitis-complement-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.