A case series of autoimmune diseases accompanied by incidentally diagnosed monoclonal gammopathy: is there a link between the two diseases?

Aim: Although the etiology of plasma cell dyscrasia is poorly understood, there is evidence for immune dysregulation or sustained immune stimulation playing a pivotal role in the pathogenesis of these diseases, including chronic infection and autoimmune disorders. In this study, we report four autoimmune disease cases where monoclonal gammopathy (MG) was incidentally found during follow-up.

Methods: We retrospectively reviewed the medical charts and laboratory test results in the following four cases: neuromyelitis optica, Kikuchi disease, Sjögren syndrome and ankylosing spondylosis.

Results: The four patients were older than 55 years and the male-to-female ratio was 2 : 2. The autoimmune disease in each case developed differently because two patients had coincidental detection of MG, whereas MG was detected 2 years and 10 years after diagnosis in the other two patients. The amount of M-components in the blood for two cases was ≤ 1 g/dL. For the other two subjects, M-components were ≥ 3 g/dL.

Conclusion: A high prevalence of MG of undetermined significance (MGUS) has been noted in a series of patients with immune disorders, suggesting a possible association with MG. Further studies should focus on determining how MG relates to various clinical information and laboratory parameters, such as disease duration, disease activity and higher sedimentation rate. In the future, we also need to identify which stimuli, such as cytokine types and levels, can induce lymphocyte clonal transformation and the production of monoclonal antibodies.