| Treatment and prognosis of IgA nephropathy | ||
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Author Daniel C Cattran, MD Gerald B Appel, MD |
Section Editor Richard J Glassock, MD, MACP |
Deputy Editor Alice M Sheridan, MD |
INTRODUCTION — IgA nephropathy is the most common cause of primary (idiopathic) glomerulonephritis in the developed world [1-4] . Although this disorder was initially thought to follow a benign course, it is now recognized that slow progression to end-stage renal disease (ESRD) occurs in up to 50 percent of affected patients [5] . The remaining patients enter a sustained clinical remission or have persistent low grade hematuria or proteinuria. However, the prognosis is quite variable and the outcome difficult to predict with accuracy in individual patients.
The classic presentation of IgA nephropathy is that of gross hematuria, often recurrent, following shortly after an upper respiratory infection [3,6] . However, the majority of patients are diagnosed following an evaluation for asymptomatic microscopic hematuria and/or mild proteinuria. Less common presentations are nephrotic range proteinuria with or without nephrotic syndrome and rapidly progressive glomerulonephritis and, rarely, malignant hypertension. The diagnosis is usually suspected based upon the clinical history and laboratory data, but can only, at the present time, be confirmed with a kidney biopsy.
The prognosis and treatment of IgA nephropathy will be reviewed here. The causes, pathogenesis, and diagnosis of this disorder, and the outcomes in patients who undergo renal transplantation, are discussed separately. (See "Causes and diagnosis of IgA nephropathy" and see "IgA nephropathy: Recurrence after transplantation")
PROGNOSIS — Patients
with IgA nephropathy and little or no proteinuria (<500 mg/day)
have a low risk of progression in the short term. However, renal
insufficiency and proteinuria develop in a substantial
proportion of patients over the long term, and such patients may
progress to end-stage renal disease (ESRD) . The possible
role of persistent microscopic hematuria in predicting an
adverse outcome in this group of patients is debated.
Frequency of progression — The natural history
of patients who present with isolated hematuria (ie, without
abnormal proteinuria) patients is not as benign as initially
thought. This was demonstrated in the following studies:
In a Chinese study of 72 consecutive patients
with IgA nephropathy who underwent diagnostic biopsy because of
hematuria with no or minimal proteinuria (defined as less than
0.4 g/day), patients were followed for a median of seven years . Protein excretion above 1000 mg/day, hypertension, and/or
impaired renal function (serum creatinine concentration ≥1.4 mg/dL
[120 µmol/L]) developed in 33, 26, 7 percent, respectively.
Clinical predictors of progression — As in other
glomerulopathies, patients who will develop progressive disease
typically have one or more of the following clinical or
laboratory findings at diagnosis
Elevated serum creatinine concentration at
diagnosis — Patients who reach a serum creatinine concentration
≥2.5 mg/dL (221 µmol/L) generally continue to progress.
Hypertension — Hypertension is associated with
arteriosclerosis and tubulointerstitial changes on biopsy, and
usually significant proteinuria.
Persistent protein excretion above 500 to 1000
mg/day.
The relation between increasing proteinuria and
a worse prognosis is probably in part a reflection of
proteinuria being a marker for the severity of glomerular
disease. The rate of progression is very low among patients
excreting less than 500 mg/day, and is fastest among those
excreting more than 3.0 to 3.5 g/day of protein [9,21,22] .
The importance of the magnitude of proteinuria
on the course of IgA nephropathy was evaluated in an
observational study of 542 patients [22] . The rate of decline
in renal function was 25-fold faster in those with sustained
proteinuria of greater than 3 g/day As described below,
ACE inhibitors or angiotensin II receptor
blockers are the preferred antiproteinuric drugs.
(See "Angiotensin inhibition" below).