Detection, significance and treatment of paraprotein in patients presenting with 'idiopathic' proteinuria without myeloma.

This paper describes the detection of a paraprotein in blood or urine in 12 of 260 patients with 'idiopathic' proteinuria, most of whom presented with the nephrotic syndrome. None had myeloma at presentation and only two have developed it. Initial clinical and biochemical findings did not suggest paraprotein-associated disease, total serum globulins and individual immunoglobulin levels usually being in the normal range. In seven of the 12 cases the paraprotein was detected only after repeated analysis of serum and urine specimens over months or years. Renal histopathology varied from case to case and is described in detail; amyloid deposition did not occur in patients who excreted kappa chain Bence Jones protein and was extensive in only three. One of these eventually developed myeloma. Patients were aged 27--69 years at onset and were observed without specific therapy for up to 56 months. Glomerular filtration rate tended to decline and proteinuria persisted. All patients have now been treated by a chemotherapeutic regimen consisting of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), cyclophosphamide, melphalan, and prednisolone, in repeated short courses. In some patients, particularly those who had kappa Bence Jones protein, there was striking improvement. Overall survival is good, eight patients being alive 17--90 months after the onset of symptoms. The importance of repeated search for paraprotein in apparently idiopathic renal disease in adults is emphasized.