IgANephropathie

IgA nephropathie, also known as IgA nephropathy or Berger disease, is the most common primary glomerulonephritis worldwide. It is characterized by predominant deposition of IgA-containing immune complexes in the glomerular mesangium, leading to mesangial proliferation and variable inflammation and scarring.

Epidemiology and presentation are heterogeneous. It often affects adolescents and young adults, with a male predominance. Many patients have a slowly progressive course, while others present with episodic gross hematuria following mucosal infections or with persistent microscopic hematuria and proteinuria.

Pathophysiology is multifactorial. Circulating galactose-deficient IgA1 forms immune complexes that deposit in the mesangium. These deposits activate the complement system, particularly C3, causing mesangial cell activation and matrix expansion. Genetic predisposition and environmental factors contribute to risk and progression.

Clinical features include episodic gross or microscopic hematuria, often coinciding with infections, and varying levels of proteinuria. Hypertension and reduced kidney function may be present, particularly in more advanced disease.

Diagnosis relies on kidney biopsy for confirmation. Light microscopy typically shows mesangial proliferation or expansion, and immunofluorescence reveals dominant IgA deposition in the mesangium, with C3 sometimes present. Electron microscopy shows mesangial immune deposits. The Oxford classification (MEST-C) describes histologic features: Mesangial hypercellularity, Endocapillary hypercellularity, Segmental sclerosis, Tubular atrophy, and Interstitial fibrosis.

Treatment focuses on slowing progression and managing complications. Blood pressure control with ACE inhibitors or ARBs and reduction of proteinuria are central. Immunosuppressive therapy, such as corticosteroids, may be considered in selected high-risk patients after benefit-risk assessment. Regular monitoring of kidney function and proteinuria is essential.