[Renal impairment in monoclonal gammapathies. Clinical study]

Renal involvement is an important and frequent complication in patient with monoclonal gammapathy (MG), especially in multiple myeloma (MM). Light chain proteinuria produces many renal manifestations, the most serious form is acute renal failure, which occurs in 5-10% of patients with MM. The frequency and form of renal involvement was determined in a group of patients with MG. The disturbances observed were correlated with the concentration and type of paraprotein in serum and urine.

We investigated 82 patients, 37 men and 45 women with an average age of 63.5 years. Apart from standard nephrologic tests the aminoaciduria/24 h and urine acidification capacity was determined. In some patients renal biopsy was performed. Proteinuria was observed in 66 cases (80.5%), in 54 of them of Bence-Jones type. Nephrotic syndrome developed in 4 patients, in all cases the renal amyloidosis was present. Renal insufficiency was diagnosed in 39 patients (47.5%), mostly in MM. In 14 cases was renal insufficiency reversible, in 14 remain stable and in 11 progressed during the course of disease. Irreversible progression developed in terminal phase of disease in most cases. Acute renal failure was observed in 6 patients, only in four of them further course of renal disease could be evaluated. In half of these 4 patients the renal failure was reversible.

Higher frequency of proteinuria and renal insufficiency was detected in patients with light chain paraprotein of lambda type, or biclonal kappa+lambda type. Aminoaciduria was diagnosed in 40% of patients, we did not observe complete Fanconi's syndrome. Incompleted form of renal tubular acidosis we diagnosed in 52% of cases without other signs of renal involvement.