Neurological manifestations of MGUS

Abstract Monoclonal gammopathy of undetermined significance (MGUS) is a highly prevalent disorder characterized by a small bone marrow plasma cell or lymphoplasmacytic clone (less than 10%) that produces a small amount of monoclonal paraprotein without associated organ damage. Most patients with MGUS display benign behavior indefinitely, but some progress to an overt malignancy, and others develop organ damage despite no increase in monoclonal protein, resulting in the so-called MG of clinical significance (MGCS). This concept includes different disorders depending on the organ involved, and among them, MG of neurological significance (MGNS) constitutes a real challenge from both a diagnostic and therapeutic point of view. Diagnosis is particularly difficult due to MGNS's heterogeneous clinical presentation and common lack of a diagnostic biopsy. On the other hand, the complexity of treatment lies in the lack of standardized regimens and the common irreversibility of neurological damage. Focusing on the neurological manifestations of MGUS affecting the peripheral nervous system, we describe 3 illustrative cases from daily practice and discuss different aspects of diagnosis to treatment, emphasizing the need for multidisciplinary management based on the close collaboration of neurologists and hematologists.