Monoclonal Gammopathies of 'Neurological Significance': Paraproteinemic Neuropathies

Objectives: To study the clinical profile and outcomes of patients with paraproteinemic neuropathy (PPN) and to explore the utility of nerve conduction studies (NCSs) to differentiate between the demyelinating subtypes. Methods: We did a retrospective analysis of patients diagnosed with PPN between January 2010 and December 2019 in an inpatient setting. The study population consisted of patients above 16 years of age presenting with clinical features suggestive of chronic peripheral neuropathy and on evaluation was found to have PPN. Results: A total of 74 patients were identified. The patients were predominantly in the 6th decade, and the majority were males. The subtypes of PPN were monoclonal gammopathy of undetermined significance (MGUS) (45.9%), POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, and skin changes) (24.3%), solitary plasmacytoma (17.6%), multiple myeloma (8.1%), and AL amyloidosis (4.1%). There are specific features on NCS which can help in identifying POEMS syndrome and IgM MGUS. The majority of patients with PPN tend to stabilize or improve with treatment; however, many have a severe residual disability. New terminology and classification of these entities as 'monoclonal gammopathies of neurological significance' can aid in early diagnosis and the development of effective treatment, to prevent residual disability. Conclusion: PPN has a heterogeneous spectrum of clinical, biochemical, and electrophysiological features. NCS can help distinguish POEMS syndrome and IgM MGUS from other demyelinating subtypes.