Chemotherapy with stem cell transplantation is more effective than immunotherapy in sporadic late onset nemaline myopathy with monoclonal gammopathy

Sporadic late onset nemaline myopathy (SLONM) is a rare proximal myopathy with an insidious onset and slow progression. Patients present initially with a proximal limb weakness. Most commonly dyspnea, dysphagia, facial muscle weakness, and cardiomyopathy develop with disease progression. If not treated, SLONM could result in 40% mortality within the first 12 months. In approximately half of the reported cases SLONM is associated with plasma cell disorders, mostly monoclonal gammopathy of unknown significance (MGUS) and anecdotally with multiple myeloma and light chain deposition disease [ 1 , 2 , 3 ]. SLONM associated with a monoclonal gammopathy (SLONM + MGUS) has an aggressive course of the disease, more severe weakness, earlier development of dysphagia and dyspnea, and overall carries an unfavourable prognosis [ 1 , 2 ]. Two approaches are used to treat SLONM + MGUS: (1) immunosuppressive therapy (steroids, steroid-sparing agents, intravenous immunoglobulins (IVIG), and plasmapheresis/plasma exchange) or (2) chemotherapy followed by autologous stem cell transplantation (ASCT). Due to the rare nature of the disease, the best treatment modality is unknown.