Selcen, Duygu

ABSTRACT Background Agrin‐congenital myasthenic syndrome ( AGRN ‐CMS) is a rare, heterogeneous genetic disorder of the neuromuscular transmission that can present from infancy to adulthood. The clinical phenotype includes distal weakness mimicking distal myopathies. Additionally, electromyography and muscle biopsy may demonstrate myopathic features, increasing the diagnostic challenge. Mitochondrial dysfunction has not been reported in the muscle of AGRN ‐CMS patients. Methods We report the clinical, electrophysiological, radiological, myopathological, and genetic findings of a patient with AGRN‐ CMS. Results A 47‐year‐old male presented at age 18 with sudden onset of eyelid ptosis, weakness, and fatigue, followed by dysphagia, dyspnea on exertion, exercise intolerance, and myalgias. Three sisters had similar symptoms. Neurological examination showed lower limb weakness, predominantly affecting the calf muscles with associated atrophy. Tendon reflexes were normal but absent at the ankles. Creatine kinase levels were normal. Electromyography demonstrated myopathic changes in distal muscles with fibrillation potentials in the gastrocnemius. 2 Hz‐Repetitive nerve stimulation of the fibular nerve revealed a 32% decrement in the extensor digitorum brevis without facilitation. Tibialis anterior biopsy showed non‐specific myopathic changes, neurogenic features, and histological evidence of mitochondrial dysfunction, as suggested by the scattered cytochrome c oxidase‐negative fibers. Whole exome sequencing detected a homozygous pathogenic AGRN variant (c.5012G>A, p.Arg1671Gln). No pathogenic or suspected pathogenic variants were detected in muscle mitochondrial DNA or in nuclear genes affecting mitochondrial function. Conclusions This patient expands the pathological spectrum of AGRN ‐CMS to include mitochondrial dysfunction and highlights the importance of low‐frequency repetitive nerve stimulation in the assessment of patients with distal weakness for differentiating myopathies from CMS.

ABSTRACTIntroduction/AimsHealthcare utilization and costs in myotonic dystrophy (DM) are not well understood. This study describes the burden of DM and its associated costs.MethodsWe performed a retrospective study using data from a large U.S. administrative claims database to identify commercially insured individuals with DM and compared healthcare utilization and cost with a matched cohort. Analyses were performed between the cohorts with ≥ 3 years of insured follow‐up.ResultsWe identified 1182 DM individuals with coverage at least 3 year prior and 3 years following an index DM diagnosis from January 1, 2009 to December 31, 2018. Compared to controls, DM individuals were 3.7 times more likely to be hospitalized (p < 0.0001), 2.4 times more likely to visit an emergency department (p < 0.0001), and had twice as many outpatient visits (p < 0.0001) in the first year post‐diagnosis, with similar utilization at 2‐ and 3‐years post‐diagnosis. Annual mean costs were 3.9 times higher for health plan paid costs (p < 0.0001) and 2.6 times higher for patient‐paid costs (p < 0.0001) for DM individuals than controls in the first year post‐diagnosis, with similar costs at 2‐ and 3‐years post‐diagnosis. Factors associated with higher costs included the need for durable medical equipment, including gait aids or respiratory support devices.DiscussionIndividuals with DM experience significantly higher healthcare utilization and associated healthcare costs than controls of similar age, sex, race, and census region. The findings show the high clinical and economic burden of DM, highlighting the importance of improving cost‐effective care delivery in this population.

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