Unusual association of multiple sclerosis with monoclonal gammopathy of undetermined significance (MGUS): two case reports.

We present two patients with demyelinating disease meeting the diagnostic criteria for multiple sclerosis. Both patients had IgG lambda monoclonal gammopathy in serum and cerebrospinal fluid associated with intrathecal antibody synthesis. This association is very unusual and it is not certain whether the co-occurrence of these disorders might be the result of a causal link between multiple sclerosis and monoclonal gammopathy or a fortuitous phenomenon.