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Neuromuscular Junction Disorders
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Diana Mnatsakanova, Qin Li Jiang
Congenital myasthenic syndrome (CMS) is a heterogeneous group of disorders caused by various genetic mutations resulting in failed neuromuscular transmission. CMS should be considered in the differential diagnosis in seronegative myasthenia especially when there is a positive family history or the onset of symptoms is in infancy or at a young age.
Neurology
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
Fenella Kirkham, Adnan Manzur, Stephanie Robb
Congenital myasthenic syndromes (CMS) are inherited (usually recessively except for slow channel syndromes). Mutations in at least 19 genes cause pre- and postsynaptic abnormalities. The commonest are postsynaptic disorders, including: AChR deficiency due to mutations in CHRNE, encoding the epsilon AChR subunit.CMS due to mutations in RAPSN.‘Limb girdle’ CMS due to mutations in DOK7.
Physiology, Biochemistry, and Pathology of Neuromuscular Transmission
Published in Marc H. De Baets, Hans J.G.H. Oosterhuis, Myasthenia Gravis, 2019
The CPSC syndrome may be identical to some cases with a congenital form of myasthenia characterized by reduced AChRs, but, in contrast to acquired MG, with a normal ACh content.181 Unfortunately, ultrastructure has not been studied in this group of patients. They seem to form a heterogeneous group, including a patient with reduced MEPPs but with a normal content of AChRs (see also under Congenital myasthenic syndrome with abnormal ACh/AChR interaction in Chapter 4).
Infantile and Early Acquired Ophthalmoplegic Syndromes
Published in Journal of Binocular Vision and Ocular Motility, 2018
Myasthenia has an infantile onset in 7–10% of cases,19 and congenital myasthenic syndromes were recently reviewed in detail by Abicht and colleagues.20 Ptosis is present in the majority of affected infants. Myasthenia may present in infancy as an autoimmune phenomenon or with a genetic etiology. In one study, about half of patients with infantile-onset myasthenia (aged 0–4) had positive testing for anti-acetylcholine receptor (AChR) antibodies.19 In congenital myasthenic syndrome, inheritance is autosomal recessive, with one study reporting a preponderance in boys.21 Autoimmune testing may be performed as in adults, testing for anti-AChR and anti-MuSK (muscle-specific kinase) antibodies. A congenital myasthenic syndrome genetic testing panel (which includes sequencing of 20 or more genes) may be submitted to confirm a genetic etiology.20 If laboratory testing is negative and clinical suspicion remains strong, electromyography with repetitive nerve simulation may be considered, though this may only be positive in 20% of patients.19 An empiric trial of pyridostigmine (starting at 3.5 mg/kg/day divided in three doses and increasing to a maximum of 7 mg/kg/day) may be initiated as both a diagnostic and therapeutic maneuver.
Electrophysiologic evaluation of myasthenia gravis and its mimics: real-world experience with single-fiber electromyography
Published in Hospital Practice, 2022
Anthony Khoo, Hnin Hay Mar, Maria Victoria Borghi, Santiago Catania
Myasthenia mimics who had an abnormal SFEMG included one case of peripheral neuropathy. This individual had been referred with concern for a slow channel congenital myasthenic syndrome with variability of strength on exertion and with temperature, together with clinical evidence of post-tetanic myokymia. Nerve conduction studies (NCS) revealed normal sensory studies, but attenuated left median and ulnar CMAPs, with acute and chronic denervation changes in upper limb muscles. Given the clinical question, tests for neuromuscular junction pathology were completed even though routine studies were convincing for a neurogenic process.
The use of frontalis sling in the management of variable ptosis secondary to congenital myasthenic syndrome
Published in Orbit, 2022
Yiran Tan, David S Curragh, Dinesh Selva
Congenital myasthenic syndrome (CMS) describes a group of rare inherited disorders caused by impaired neuromuscular transmission at the motor endplate.1 Common ophthalmic manifestations associated with CMS include varying degrees of ptosis and ophthalmoplegia.2 The authors describe a case of variable ptosis secondary to congenital myasthenic syndrome managed with bilateral silicone frontalis slings. Patient consent has been obtained for publication of the report.