IgA nephropathy (IgA nephropathy) refers to a glomerular disease characterized by predominant IgA deposition in the mesangial region of the glomeruli, hence also known as mesangial IgA nephropathy. Clinically, it mainly manifests as recurrent hematuria associated with infections, often accompanied by grade I proteinuria. Most cases remain stable, while a few patients may develop nephrotic syndrome. IgA nephropathy is relatively common, accounting for approximately 20-40% of primary glomerular diseases. It predominantly occurs in children and young adults, with a higher incidence in males than females. About 10-30% of patients may progress to chronic renal insufficiency.

bubble_chart Etiology

More than half of the patients with this disease exhibit elevated serum IgA levels. Immunopathological examination reveals deposits of IgA, IgG, and C3 in the glomerular mesangial area and the walls of skin capillaries, without the presence of early complement components, indicating that IgA nephropathy is an immune complex-mediated glomerulonephritis. In three-quarters of the patients, the disease onset follows respiratory or digestive tract infections, accompanied by elevated serum IgA levels, which is caused by the immune response of epithelial cells in the affected mucosa secreting IgA. Animal experiments demonstrate that macromolecular polymeric IgA or IgA-IgG immune complexes play a role in the pathogenesis and progression of this disease. When the function of hepatocytes and the mononuclear phagocyte system is impaired, reducing their clearance capacity, these macromolecular immune complexes deposit from the bloodstream into the glomeruli, leading to IgA nephropathy.

It is more common in adolescents, particularly males. Most patients experience upper respiratory or digestive tract infections before onset, followed by gross hematuria within hours to days. Gross hematuria occurs in 40% of all cases and can be either transient or recurrent. Most patients show no systemic symptoms, though some may experience general discomfort, muscle and lumbar soreness, and occasionally dysuria and urinary frequency. Patients with recurrent hematuria often have microscopic hematuria between episodes, typically accompanied by grade I proteinuria, with 24-hour urinary protein excretion below 1–2 g. Only about 10% of patients exhibit daily proteinuria exceeding 3 g, presenting as nephrotic syndrome. Blood pressure is mostly normal, and acute renal failure occurs occasionally. Approximately 2–3% of patients progress to end-stage renal failure annually.

bubble_chart Auxiliary Examination

Urinalysis shows varying degrees of hematuria, with most urinary red blood cells being deformed and showing spicules, indicating glomerular hematuria. Most cases present with small amounts of urinary protein, occasionally with massive proteinuria. Approximately half of the patients exhibit transient elevation of serum IgA, while IgG and IgM levels are normal or slightly elevated. Serum C3 and C4 concentrations are normal. About 10% of patients experience a gradual increase in serum creatinine, leading to progressive renal dysfunction.

bubble_chart Diagnosis

Episodic or transient gross hematuria accompanied by elevated serum IgA levels should raise suspicion of this disease, with confirmation relying on renal biopsy. Pathologically, not all IgA deposits in the glomerular mesangial region constitute IgA nephropathy.

There is currently no specific treatment. During the acute stage of an attack, bed rest is recommended, with symptomatic treatment as the main approach, such as controlling infections and treating hypertension. For cases where hematuria episodes are closely related to tonsil infections, a tonsillectomy may be considered. For those presenting with nephrotic syndrome, hormone and immunosuppressive therapy can be used. Animal experiments have shown that using α-penicillamine to dissociate circulating immune complexes, neomycin to alter gut flora, or phenytoin sodium and prostaglandin E to reduce blood IgA levels can halt disease progression, but clinical trials have not confirmed definitive efficacy.

bubble_chart Prognosis

Patients with persistent proteinuria or significant proteinuria presenting as nephrotic syndrome have a poor prognosis; diffuse proliferative glomerulonephritis with focal crescent formation is prone to progress to renal insufficiency; grade III mesangial proliferation or global sclerosis also indicates a poor prognosis; adults with hypertension, hematuria accompanied by massive proteinuria have an unfavorable prognosis. On average, hypertension may develop after 6 years, and dialysis may be required after 20 years. Reports indicate that 10% of patients undergo kidney transplantation, with IgA nephropathy recurring in the transplanted kidney within 3 months to 3 years.

bubble_chart Differentiation

The renal biopsy findings of Henoch-Schönlein purpura, systemic lupus erythematosus, Sjögren's syndrome, and alcoholic cirrhosis can resemble those of IgA nephropathy, so differentiation still requires a combination of disease history and clinical manifestations.