Asymptomatic immunoglobulin light chain amyloidosis (AL) at the time of diagnostic bone marrow biopsy in newly diagnosed patients with multiple myeloma and smoldering myeloma. A series of 144 cases and a review of the literature

The rate of asymptomatic amyloidosis (AL) among patients with newly diagnosed multiple myeloma (MM) or smoldering multiple myeloma (SMM) is unknown. We evaluated number and clinical significance of asymptomatic AL in consecutive MM and SMM patients, not having recognition of symptomatic AL at the time of their diagnostic bone marrow biopsy. Bone marrow biopsies were stained with Congo red and considered diagnostic for AL in case of positive Congo red staining with apple-green birefringence. Biopsies from 144 patients were evaluated: 77 had a diagnosis of MM and 67 of SMM. The median age was 59 (range 26-84) years; the median follow-up was 76 months (range 0-216). Immunoglobulin isotypes were 96/144 (67%), IgG; 23/144 (16%), IgA; 12/144 (8%), light chain only; 1/77 (1%), IgD; and biclonal or indeterminate, 12/144 (8%). Fifty-eight percent (84/144) were kappa restricted. The presence of amyloid was found in two cases (1%, 95% CI -0.6 to 3.2), one in MM, and one in SMM group, and none had or developed signs or symptoms suggestive of organ involvement by amyloid. Among the 142 other patients without amyloid deposition in their index bone marrow, one (0.7%, 95% CI -0.6 to 2.0) developed symptomatic AL after 119 months.