Late onset systemic lupus erythematosus and lupus-like disease in patients with apparent idiopathic glomerulonephritis.

We report 17 patients who presented with either apparent idiopathic glomerulonephritis (16 patients) or post-streptococcal glomerulonephritis (one patient). Doubts arose about the nature of these patients' disease, either because their initial renal histology was suggestive of systemic lupus erythematosus (SLE) in the absence of its clinical or serological features, or because they developed with time the clinical or serological features of SLE. Three patients had a positive antinuclear antibody (ANA) test at the onset of their illness, but normal levels of serum binding of double-stranded DNA (dsDNAB). In another four patients the dsDNAB was slightly raised but with a negative ANA. On renal biopsy the predominant appearance was membranous glomerulonephritis (GN) in 10, subendothelial mesangiocapillary GN (MCGN) in three, and focal segmental glomerulosclerosis in two; one patient each had a focal proliferative GN and a diffuse endocapillary GN. On 1 micron renal sections stained with toluidine blue, 10 patients had immune deposits at multiple sites within the glomeruli. Over a period of one to 14 years, six patients developed extrarenal features suggestive of SLE, nine a positive ANA, and 12 increased serum levels of dsDNAB. Five patients became hypocomplementaemic. Cryoglobulins were isolated from the sera of 10 out of 12 patients; seven contained DNA. Separated cryoglobulin IgG from eight patients showed antibody activity directed against both ss and dsDNA in four, and against dsDNA only in three. On the basis of the clinical, histological and serological observation during follow-up five patients were reclassified as definite SLE, four as probable SLE and two as possible SLE. Rarely, SLE may present with nephritis as the sole disease manifestation, antedating other clinical features and even immunological markers of the disease by years. In addition, some patients with a glomerulonephritis may show clinical and immunological, or histological features of SLE, but do not fit accepted definitions of the disease.