Efficacy of multimodality therapy for sporadic late onset nemaline myopathy and associated monoclonal gammopathy

Sporadic late-onset nemaline myopathy (SLONM) is a rare adult-onset disorder leading to muscle weakness, first reported in 1966. The disease is closely associated with plasma cell disorders, particularly monoclonal gammopathy (MG), but does not have a standardized treatment approach despite fatal outcome in several reported cases. In this report, a male patient diagnosed with SLONM-MGUS was treated using various modalities over several years, including intravenous immunoglobulin (IVIg) and monoclonal anti-CD 20 antibody, rituximab, and on progression, received a multi-modality treatment strategy with high-dose melphalan chemotherapy and autologous hematopoietic cell transplant (ASCT), followed by maintenance with immunomodulatory agent (IMiD), lenalidomide. He underwent ASCT in April 2018 (age 53) and, at the time of reporting (age 60), has maintained clinical benefit for more than seven years on lenalidomide maintenance. While prior therapies provided transient improvement, ASCT followed by maintenance therapy was associated with durable functional benefit. The study emphasizes the need to correctly diagnose this rare disorder and the potential benefit of multi-modality strategy including ASCT followed by lenalidomide maintenance in treating SLONM-MGUS and indicates that the disappearance of monoclonal protein is not always linked to neurological recovery. Our patient adds further evidence to the existing literature and demonstrates sequential clinical benefit from various modalities including IVIg, rituximab, ASCT, and IMiDs in this rare disorder.