# Immunoglobulin A Nephropathy With Associated Thrombotic Microangiopathy: Biopsy and Clinical Case Series

## TL;DR

This study examines a rare and severe kidney disease combination involving IgA nephropathy and thrombotic microangiopathy, linked to complement system dysregulation.

## Contribution

The study identifies a unique IgA nephropathy phenotype associated with TMA and complement activation, suggesting a more severe clinical course.

## Key findings

- Seven patients with IgA nephropathy and TMA showed severe hypertension, proteinuria, and low eGFR.
- Complement system dysregulation was indicated by low C3, high C4, elevated CH50 in six out of seven patients.
- Interstitial fibrosis and tubular atrophy were common, suggesting a chronic progression of the disease.

## Abstract

IgA nephropathy (IgAN) with concurrent thrombotic microangiopathy (TMA) is an unusual combination of pathological findings that is associated with severe hypertension, proteinuria, and lower estimated glomerular filtration rate (eGFR). This series presents 7 patients with kidney biopsies demonstrating IgAN and concomitant TMA and presents a link by way of complement disorder.

Seven patients all presented as IgAN with associated TMA coinciding with hypertension, proteinuria, and low eGFR. Six patients showed tubular atrophy or interstitial fibrosis and 5 of those 6 showed >50% of renal cortex containing tubular atrophy or interstitial fibrosis. Variations of low serum C3, high serum C4, elevated IgA or IgM proteins, and elevated CH50 were found in 6 of the 7 patients.

Chronic changes seen like interstitial fibrosis and tubular atrophy appear to show a subacute or chronic nature of IgAN with TMA. The low serum C3, high C4, elevated CH50, suggests complement activation in endothelial and mesangial from IgG-IgA complexes known to occur in IgAN. This phenotype of IgAN with TMA may represent a more unique IgAN phenotype with a more severe clinical course and be indicative of underlying complement dysregulation.