Characterization of monoclonal gammopathy in patients with amyotrophic lateral sclerosis.

BACKGROUND: Recently, new guidelines for the monitoring and the risk evaluation of monoclonal gammopathy with undetermined significance (MGUS) became available and the light chain MGUS subtype was defined.

AIMS OF THE STUDY: To characterize the type, risk and diagnostic implications of MGUS in patients with amyotrophic lateral sclerosis.

METHODS: We screened 97 consecutive patients with ALS and 97 age- and gender-matched controls for MGUS by serum electrophoresis and immunofixation and compared the characteristics of MGUS with population-based data.

RESULTS: MGUS was identified in 8.2% of ALS patients and 6.2% of controls (mean age: 62.5 years both). Seven of eight ALS patients with MGUS had 'low-risk MGUS'. M-protein was moderately increased in one ALS patient. The immunoglobulin distribution in ALS patients with MGUS was IgG kappa (n = 2), IgM lambda (n = 1) and light chains of lambda type (n = 3). No differences in demographic and clinical parameters were found between patients with and without MGUS.

CONCLUSIONS: The percentage of patients with MGUS is increased in ALS, but the immunoglobulin distribution is similar to that reported in the general population. MGUS in ALS mostly represents 'low-risk MGUS'; therefore, unnecessary diagnostic procedures should be avoided in ALS patients.