Renal outcome and monoclonal immunoglobulin deposition disease in 289 old patients with blood cell dyscrasias: a single center experience.

Monoclonal components (MC) formed by chains/fragments of intact/truncated globulin components produced in different lymphoproliferative diseases are responsible for monoclonal immunoglobulin deposition disease (MIDD) and consequent tissue damage by organized (amyloid fibrils) or non-organized (amorphous) deposits. The kidneys are the most commonly affected organs in MIDD, and renal failure represents an important adverse factor for prognosis. The renal outcome and the role of renal pathology in diagnosing MIDD was evaluated in 289 elderly patients with multiple myeloma (MM, n=115) and monoclonal gammopathy (MGUS, n=174). Renal impairment was the only significant risk factor for patient death, while significant risk factors for renal impairment were diabetes (HR 3.65, 95% CI: 2.08-6.41), light chain (LC) proteinuria (HR 2.18; 95% CI: 1.10-4.32) and type of MC (p=0.0019). Renal pathology documented MIDD in 12/30 cases (40%): six cases of AL-amyloidosis, two of LC disease, one of heavy chain disease and three of cast nephropathy, as well as four cases of glomerulonephritis, eight of arteriolosclerosis and six of normal picture. Main conclusions are that diabetes, sharing common glomerular damage with LC disease, is the strongest risk factor for progression of renal disease, and glomerular proteinuria or heavy LC proteinuria should raise a strong suspicion index of MIDD and prompt pathology assessment to reach the correct diagnosis.