Idiopathic immunoglobulin A (IgA) nephropathy, or Berger disease, is a worldwide primary glomerulonephritis first described by Berger and Hinglais in 1968, based on the finding of predominant IgA deposition in the mesangium with a mesangial proliferation. The clinical spectrum varies from asymptomatic microhematuria to rapidly progressive glomerulonephritis. The vast majority of patients are characterized by recurrent episodes of gross hematuria, which usually occurs in concomitance with mucosal infections of the upper respiratory tract or other infections, or by asymptomatic microscopic hematuria with or without proteinuria.
Although it can present at any time, the peak incidence of disease is in the second and third decades of life. A male-to-female ratio of 2:1 is observed in North American and Western European populations, although this difference is not observed among populations in the Pacific.
IgA nephropathy occurs with greatest frequency in Asians and whites and is relatively rare in blacks. In a Chinese study, IgA nephropathy constituted 45% of all cases of primary glomerulonephritis.
However, IgA deposits may also be seen on kidney biopsy findings in individuals with no evidence of renal disease. The reported incidence rate of mesangial IgA deposition in apparently healthy individuals is 3-16%. These cases had no clinical features of nephritis, but their renal biopsy findings were consistent with IgA nephropathy.
Spontaneous remission has been reported in children and adults. Secondary IgA nephropathy is also associated with various underlying disease processes. It was initially considered a benign condition, but extended follow-up indicates that IgA nephropathy does lead to significant kidney damage, and progressive disease develops in 20-30% of children 15-20 years after disease onset. Advanced age, hypertension, proteinuria, and impaired renal function at presentation are poor prognostic indicators.