DOPA-Responsive Tremor Associated With Gammopathy: A Case Report and Literature Review.

Tremors have been well-described in association with monoclonal gammopathy. We report a case of a patient with asymmetric hands tremor who responded well to levodopa-carbidopa treatment. Further workup showed an underlying gammopathy. To our knowledge, this is one of the rarest case reports of successful treatment of gammopathy-related tremors with levodopa-carbidopa. The patient was a 75-year-old male who presented to the neurology clinic for a one-year history of worsening tremors in bilateral upper extremities. A review of systems was only remarkable for mild numbness and tingling in his feet. His neurological examination was remarkable for asymmetric right more than left (R > L) resting and kinetic tremor in both upper extremities associated with mild rigidity and bradykinesia in right upper extremity and decreased bilateral ankle jerks. With the primary diagnosis of Parkinson's disease, he was started on levodopa-carbidopa and a neuropathy workup was requested. His follow-up visit after three months was remarkable for significant improvement of his tremors with carbidopa-levodopa. However, his blood work was consistent with a significant increase in lambda light chain levels and the presence of an M spike in serum protein electrophoresis. Based on the presentation and clinical workup, he was finally found to have both multiple myeloma and ​Waldenstrom's macroglobulinemia. Underlying malignancy was treated with chemotherapy and immunotherapy. Levodopa-carbidopa was discontinued after three months of chemotherapy and his tremor did not recur in one year of follow-up. Gammopathy is one of the well-known causes of tremors in the adult population. It can cause both resting and kinetic tremors in the upper extremities. It is supposed that peripheral neuropathy associated with gammopathy is the main underlying cause of tremors in these groups of patients. However, central causes are also suggested. In this case, we are led to conclude that our patient's tremor was centrally mediated since it responded well to dopamine replacement therapy. However, further study is needed to elucidate the role of dopamine depletion in the pathogenesis of tremors associated with gammopathies.