Long-term prognosis of IgA nephropathy presenting with minimal or no proteinuria: A single center experience

The long-term prognosis of patients with IgA nephropathy (IgAN) who present with preserved renal function and minimal proteinuria is not well described. We investigated the long-term outcomes of IgAN patients with an apparently benign presentation and evaluated prognostic factors for renal survival and clinical remission. We studied Japanese patients with biopsy-proven IgAN who had an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m² and proteinuria <0.5 g/day at the time of renal biopsy. The renal biopsies were reviewed using the Oxford classification. Twenty patients met the inclusion criteria. At diagnosis, the median eGFR (interquartile range) was 76.8 (65.2–91.1) mL/min/1.73 m², and the median proteinuria level was 0.31 (0.16–0.39) g/day. Only one patient had an increase in serum creatinine of over 50% and no patient progressed to end-stage renal disease. The 15-year renal survival rate was 93.8%. Clinical remission was observed in 9 (45%) patients. Baseline proteinuria was the only factor significantly associated with the absence of clinical remission. The long-term prognosis of Japanese patients with IgAN who presents with minor urinary abnormalities and preserved renal function is excellent.

IgA nephropathy with early kidney disease is associated with increased arterial stiffness and renin-angiotensin system activity

BACKGROUND

IgA nephropathy is associated with increased cardiovascular risk, though whether this is due to loss of kidney function or proteinuria is unclear.

METHODS

For this study 10 normotensive IgA nephropathy subjects with early kidney disease (41±5 yrs, glomerular filtration rate (GFR) 87±9 ml/min, proteinuria 720±300 mg/d) and 10 gender- and blood pressure-matched healthy controls (36±1 yrs, estimated GFR 102±5 ml/min, proteinuria 70±6 mg/d) were studied in high-salt balance. Blood pressure and arterial stiffness, expressed as pulse wave velocity and aortic augmentation index, were measured at baseline and in response to 60 min of angiotensin II (AngII) infusion.

RESULTS

At baseline, IgA nephropathy subjects demonstrated similar pulse wave velocity (8.6±0.7 vs. 8.0±0.4 m/s, p=0.5) but increased aortic augmentation index (12.6±3.1 vs. 1.8±4%, p=0.04) and a trend towards increased circulating renin-angiotensin system (RAS) components (plasma renin activity, 0.55±0.18 vs. 0.21±0.05 ng/l/s, p=0.08; angiotensin II, 25±5 vs. 16±1 ng/l, p=0.08) compared with controls. However, despite similar baseline blood pressure values (p=0.8), IgA nephropathy was associated with reduced arterial sensitivity to AngII challenge (Δmean arterial pressure: 19±4 vs. 29±1 mm Hg, p=0.05; Δpulse wave velocity: -0.06±0.6 vs. 1.5±0.3 m/s, p=0.07) compared with controls, even after multivariate analysis.

CONCLUSION

Even in the setting of early kidney disease, IgA nephropathy is associated with increased arterial stiffness and decreased angiotensin II responsiveness, a marker of increased RAS activity.

Review of cases of IgA nephropathy

OBJECTIVES

A review of 26 years of British military renal pathology showed the commonest diagnosis to be immunoglobulin A (IgA) nephropathy affecting 115/346 (33%) of cases. It was possible to follow-up 50/115 military patients with this condition with the primary objective to determine whether initial observations enabled a confident prediction of prognosis. Additionally, unpublished observations have shown that the incidence of glomerulonephritis in an Indo-Asian British military racial group was fourfold that in the majority Caucasians although the nature of pathology (IgA vs non-IgA nephropathy) was not statistically significantly different. The present study secondarily sought to determine if prognosis of IgA nephropathy was different in this Indo-Asian military group. Finally, some conclusions concerning the traditionally restrictive policy towards applicants for military service with evidence of active nephritis were attempted.

METHODS

An archive of military renal patients covering 1985-2011 was reviewed and clinical details of cases of IgA nephropathy were extracted and analysed.

RESULTS

95 cases (80 Caucasian, 15 Indo-Asian) were reviewed. There was no racial difference (p=0.2) in initial median estimated glomerular filtration rate (eGFR, 86 vs 83 ml/min/1.73 m(2)). Altogether, initial median of mean arterial pressure (MAP) was 96 mm Hg (IQR=87-103) and median proteinuria was 485 mg/24 h (IQR=195-925). There was an inverse correlation between initial eGFR and both MAP (p=0.0008) and proteinuria (p=0.0006). In the 50 patients who were followed up, the change in eGFR with time (ΔeGFR) was calculated. 10 of the 44 Caucasians and 3/6 Indo-Asians showed significant changes in eGFR but population proportions were not significantly different (p=0.2). Altogether, 11/50 (22%) showed deteriorating eGFR despite therapeutic interventions, compared with those without deterioration; this was not due to different duration of observation (p=0.08), initial MAP (p=0.23) or initial proteinuria (p=0.07). There was no statistically significant correlation between ΔeGFR and initial MAP (p=0.6) or proteinuria (p=0.7).

CONCLUSIONS

The proportion of military cases of IgA nephropathy with deteriorating renal function (22%) was not different from that described in civilians, suggesting that military medical management (including operational restriction where necessary) was appropriate. Initial clinical observations, including racial group, did not permit confident prediction of prognosis thus mandating follow-up for all military cases. Relaxing current enlistment policy would be inadvisable given the inability to confidently predict prognosis in individual cases.