Immunotherapy for Respiratory Complications of Sporadic Late Onset Nemaline Myopathy (SLONM) with Monoclonal Gammopathy (P5.098)

INTRODUCTION: Sporadic late onset nemaline myopathy (SLONM) is a rare disease which can be associated with monoclonal gammopathy of unclear significance (MGUS). Nemaline myopathy, is defined on the basis of structural abnormalities of the muscle fiber, histological based on the presence of rod like bodies in the muscle fiber. Clinically SLONM appears mostly after the fourth decade of life as rapidly progressing proximal limb weakness, respiratory insufficiency, and facial and bulbar weakness. METHODS: We describe a case of SLONM associated with MGUS (Ig G kappa with free light chains) who responded to IV steroids and IVIG. CASE: 46 year old woman who presented to the ED with a 2 week history of progressive shortness of breath. She had a 2 year history of symmetric progressive painless weakness involving the face and the proximal extremities. At presentation to the ED there was significant proximal weakness in the upper extremities. In the lower extremities there was weakness without antigravity hip flexion and distally she gave effort against resistance. There was facial weakness evident in orbicularis muscles, neck flexors and extensors. The respiratory parameters showed a NIF of -20. Serum creatinine kinase, aldolase, acetylcholine receptors and HIV were normal. IgG kappa monoclonal protein was positive. An EMG demonstrated evidence of a proximal myopathic process with fibrillation potentials. Muscle biopsy demonstrated nemaline rod formations with muscle fiber atrophy and non-specific focal increased mitochondrial accumulation on electron microscopy sections (Figures). She was admitted to the ICU and received a 5 day course of IVIG and showed progressive improvement in her respiratory parameters. CONCLUSION In conclusion, the case we describe suggest that IVIG and steroids may be beneficial in the acute treatment of SLONM with MGUS and may improve functional respiratory status. Despite previous reports in which the association with monoclonal gammopathy has been related to a poor prognosis, this case illustrates that some patients may improve despite overall poor prognosis. Disclosure: Dr. Rosales has nothing to disclose. Dr. Varosanec has nothing to disclose. Dr. Lugo has nothing to disclose. Dr. Prayson has nothing to disclose. Dr. Rahmlow has nothing to disclose.