We evaluated retrospectively the presenting clinical features, response to treatment and clinical course of 19 patients with LCDD, 11 of whom had multiple myeloma. At presentation, renal insufficiency was present in 18 patients and proteinuria in 16. Renal biopsy revealed typical LCDD in 16 patients, while in the remaining three LCDD was associated with other abnormal tissue deposits. Extrarenal signs were observed in 12 patients (63%), with the liver, heart and peripheral nerves being the most frequently involved organs. After diagnosis, 18 patients underwent therapy: 2 received steroids alone and 16 were treated with steroids and cytotoxic drugs; 7 patients also underwent plasma exchange. At the end of the first month of treatment renal function improved in 5 patients, worsened in 5 and remained unchanged in 8. All but 3 of the patients continued treatment beyond the first month: 7 patients developed end-stage renal disease, 5 an improvement and 4 a worsening in renal function. No effect on proteinuria was observed. Extrarenal symptoms developed in 4 previously unaffected patients and in 3 others they extended to more organs. Sixteen patients died: 12 during the first year of the follow-up, and 4 at 21st, 34th, 37th and 82nd month of observation. Five patients died from neoplastic cachexia, 4 from hypokinetic cardiopathy, 3 from hemorrhagic complications, 2 from pneumonia and one from unknown cause. Mean patient survival after presentation was 18.1 +/- 20.7 months.(ABSTRACT TRUNCATED AT 250 WORDS)