[Sporadic Late-Onset Nemaline Myopathy Associated with MGUS]

Sporadic late-onset nemaline myopathy is an uncommon disease. Clinically, it is characterized by progressive muscle weakness that can develop in limbs or axial muscles. Asymmetrical distal weakness, facial weakness, dropped head, and dysphagia can also occur. Since the serum creatine kinase level usually remains within the normal range, patients can be misdiagnosed with motor neuron disease. Recognition of nemaline rods on muscle biopsy is crucial for accurate diagnosis. If it is associated with monoclonal gammopathy of undetermined significance, the outcome is known to be unfavorable. In spite of various immunotherapies such as corticosteroids, immunosuppressants, and plasmapheresis, most patients die of respiratory failure within 5 years. Since the efficacy of autologous stem cell transplantation following high-dose melphalan was first reported in 2008, there have been accumulating reports that showed the positive effect of this therapy for the disease.