Anti-glomerular basement membrane (GBM)-antibody-mediated disease with normal renal function.

BACKGROUND: This study compared the clinical and laboratory characteristics of patients with anti-glomerular basement membrane (GBM) disease and normal renal function, with those of patients with anti-GBM disease where there was renal impairment.
METHODS: The medical records of the 14 patients who had presented with anti-GBM disease to our hospital in the past 20 years were reviewed.
RESULTS: Five (36%) had a normal serum creatinine or creatinine clearance at presentation. Other features were haemoptysis (2/5, 40%), macroscopic haematuria (2/5, 40%) or systemic symptoms (1/5, 20%). All five (100%) had some degree of haematuria, four (80%) had proteinuria of at least 1 g/day, and none was hypertensive. Anaemia, a raised WCC, or elevated ESR (> 35 mm/h) occurred less often than in patients with impaired renal function (P<0.05). Two of the five (40%) with normal renal function had circulating anti-GBM antibodies, which were present at low or moderate levels; but seven of the nine with renal impairment (77%) had circulating antibodies, with high levels in five. Renal biopsies from patients with normal renal function were normal (1/5, 20%), showed mesangial proliferation (4/5, 80%) or had more than 20% glomeruli sclerosed (1/5, 20%). Complement deposition was present in 2/4 biopsies (50%). The kidneys from patients with renal impairment had crescents in more than 50% glomeruli (9/9, 100%), and four had more than 20% glomeruli sclerosed (44%). All four kidneys from patients with renal impairment that were examined had complement deposits (100%). Treatment was identical in both groups; patients with normal renal function were followed for a median of 48 months, and those with renal impairment for 180 months. There were no further episodes of haemoptysis, haematuria, or other symptoms of relapse in either group. All five patients with normal renal function are alive, and the serum creatinine is less than 0.2 mmol/l in all (100%), but haematuria persists in one (20%), and proteinuria >1 g/day in two (40%). Eight of the nine (89%) patients with impaired renal function survive, but all are currently being dialysed or have had a renal transplant.
CONCLUSION: Patients with anti-GBM disease with normal renal function are not uncommon, and often have a good prognosis. There is less renal damage, possibly because of lower levels of circulating anti-GBM antibodies and less glomerular complement deposition.