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Abstract: We present the electrodiagnostic findings in a case of a 3-year-old girl presenting with sensory ataxia, gait disturbance, and visual-auditory disturbance with a genetically confirmed diagnosis of riboflavin transporter deficiency type 2 (RTD2). She carries a homozygous mutation in the SLC52A2 gene, c.1016T>C (p.Leu339Pro). Her testing demonstrates a non-length-dependent axonal sensorimotor polyneuropathy affecting predominantly the upper extremities with active denervation of the distal muscles of both arms. It is important to highlight these findings because most genetic neuropathies have a length-dependent pattern of involvement, affecting the distal legs before the arms. The electrodiagnostic findings in RTD2 have not been previously well described. These electrodiagnostic findings are in agreement with the typical clinical phenotype of RTD2, which affects the upper limbs and bulbar muscles more than the lower extremities., Competing Interests: The authors report no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Muscle-specific kinase (MuSK) antibody is seen in 4%-10% of patients with myasthenia gravis (MG), with 40% of these patients reporting bulbar weakness as the initial symptom. We present the case of a 40-year-old woman with MuSK MG whose only presenting symptom was progressive respiratory insufficiency necessitating BiPAP use 16-24 hours daily. She was unresponsive to treatment for cardiac and pulmonary causes and thus referred to neurology. Initial workup directed toward autoimmune and genetic myopathies was unrevealing. MuSK antibodies were positive (60.7 nmol/L, nl 0.00-0.02). Electrodiagnostic studies were unremarkable other than single fiber electromyography which was consistent with a defect in neuromuscular transmission. Treatment with prednisone, plasma exchange, and rituximab led to improvement to reliance on BiPAP only at night. However, her most treatment refractory and quality of life limiting symptom continues to be respiratory insufficiency. Further investigation to better characterize differential response to treatment in this subset of patients with MuSK MG may be needed., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: Glutaric acidemia type II (GA II) typically presents with profound metabolic acidosis, hypoketotic hypoglycemia, and mild dysmorphic features in newborns. Since its description, 11 patients with adult-onset GA II have been reported., Case Report: A 23-year-old woman presented at 6 months gestation with preterm labor and weakness for 3 months. Her weakness worsened to the point of not being able to walk despite treatment with corticosteroids for presumed myositis. Biopsies of skeletal muscle revealed extensive lipid myopathy. Metabolic studies and urine organic acids were suggestive of a multiple acyl-CoA dehydrogenase deficiency. Immunoblot of skin fibroblasts demonstrated a deficiency of electron transfer flavoprotein-ubiquinone oxidoreductase. Treatment with carnitine, riboflavin, and diet restrictions improved muscle strength and decreased urine organic acids., Conclusion: This patient had the unique presentation of GA II with only myopathy. In adults with late-onset weakness, metabolic disorders should be considered in the differential diagnosis.