What evidence supports Henoch-Schönlein purpura (IgA vasculitis) and IgA nephropathy as distinct disorders?

Updated: Jan 08, 2021
  • Author: Rajendra Bhimma, MBChB, MD, PhD, DCH (SA), FCP(Paeds)(SA), MMed(Natal); Chief Editor: Craig B Langman, MD  more...
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Overall, the data tend to support the view that IgAV and IgA nephropathy are distinct diseases. [42] Zhou et al examined 31 children aged 3-15 years with IgA nephropathy and 120 children aged 4-15 years with IgAV, noting their clinical manifestations, blood biochemistries, serum immunology, and follow-up data. [43] Pathologic findings on light microscopy, immunofluorescence study, and electron microscopy of kidney biopsy specimens were analyzed and compared between 31 children with IgA nephropathy and 32 children with IgAV.

The age of onset was older than 12 years in 25.8% of the children with IgA nephropathy but in only 10% of those with IgAV. [43] Clinical patterns of IgA nephropathy were similar to those of IgAV, but extrarenal manifestations were observed more often in patients with IgAV. All of the IgAV patients had skin purpura, 59% had GI symptoms, and 47% had arthralgia. Of the children with IgA nephropathy, only 3.2% had abdominal pain. [43] Kidney pathology in patients with IgA nephrology versus those with IgAV was as follows:

  • Global sclerosis: 35.5% vs 3.1%
  • Mesangial sclerosis: 41.9% vs 6.3%
  • Endothelial proliferation: 29% vs 65.6%
  • Thin basement-membrane nephropathy: 6.5% vs 0%

In the kidneys of patients with IgAV, electronically dense deposits were sparse, loose, and widely spread in the glomerular mesangium, in the subendothelial area, and even in the intra-basement membranes. In those with IgA nephropathy, the deposits were dense, lumpy, and mostly limited to mesangium and paramesangium. [43]

Immunoglobulin G (IgG) was found in glomerular immune deposits in 71.9% of patients with IgAV but in only 19.4% of patients with IgA nephropathy. [43] No IgG deposit was observed in 81.6% of those with IgA nephropathy; most had IgA and immunoglobulin M (IgM) or C3 deposits. Predominant IgG deposits were found in 12.5% of IgAV patients, with relatively weak IgA deposits. Moreover, 6.3% of IgAV patients had linear IgG deposits in the glomerular capillary wall, a finding that was not noted in patients with IgA nephropathy.

The rate of complete remission was 72.5% in patients with IgAV at an average of 20 months’ follow-up; the corresponding rate was 19.4% in those with IgA nephropathy after 34 months’ follow-up. [43] Moreover, 64.5% of patients with IgA nephropathy had consistent hematuria and proteinuria, and 16.1% had active nephritides.

The important clinicopathologic differences Zhou et al found between IgAV and IgA nephropathy argue against the single-disease hypothesis.

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