MedGen

Congenital myasthenic syndromes (CMS) are a group of inherited disorders affecting the neuromuscular junction (NMJ). Patients present clinically with onset of variable muscle weakness between infancy and adulthood. These disorders have been classified according to the location of the defect: presynaptic, synaptic, and postsynaptic. CMS6 is an autosomal recessive CMS resulting from a presynaptic defect; patients have onset of symptoms in infancy or early childhood and tend to have sudden apneic episodes. Treatment with acetylcholinesterase inhibitors may be beneficial (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome associated with AChR deficiency is a disorder of the postsynaptic neuromuscular junction (NMJ) clinically characterized by early-onset muscle weakness with variable severity. Electrophysiologic studies show low amplitude of the miniature endplate potential (MEPP) and current (MEPC) resulting from deficiency of AChR at the endplate. Patients with mutations in the CHRNE gene may have compensatory increased expression of the fetal subunit CHRNG (100730) and may respond to treatment with cholinergic agents, pyridostigmine, or amifampridine (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Fast-channel congenital myasthenic syndrome (FCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the acetylcholine receptor (AChR) channel, specifically from abnormally brief opening and activity of the channel, with a rapid decay in endplate current and a failure to reach the threshold for depolarization. Treatment with pyridostigmine or amifampridine may be helpful; quinine, quinidine, and fluoxetine should be avoided (summary by Sine et al., 2003 and Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome is a disorder characterized by variable degrees of muscle fatigability caused by impaired transmission of electrical signals at the neuromuscular junction (NMJ) (summary by Arnold et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndromes (CMS) are a group of inherited disorders affecting the neuromuscular junction. Patients present clinically with onset of variable muscle weakness between infancy and adulthood. These disorders have been classified according to the location of the defect: presynaptic, synaptic, and postsynaptic. Endplate acetylcholinesterase deficiency is an autosomal recessive congenital myasthenic syndrome characterized by a defect within the synapse at the neuromuscular junction (NMJ). Mutations in COLQ result in a deficiency of acetylcholinesterase (AChE), which causes prolonged synaptic currents and action potentials due to extended residence of acetylcholine in the synaptic space. Treatment with ephedrine may be beneficial; AChE inhibitors and amifampridine should be avoided (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome associated with AChR deficiency is a disorder of the postsynaptic neuromuscular junction (NMJ) clinically characterized by early-onset muscle weakness with variable severity. Electrophysiologic studies show low amplitude of the miniature endplate potential (MEPP) and current (MEPC) resulting from deficiency of AChR at the endplate. Treatment with cholinesterase inhibitors or amifampridine may be helpful (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome-13 (CMS13) is an autosomal recessive neuromuscular disorder characterized by onset of proximal muscle weakness in the first decade. EMG classically shows a decremental response to repeated nerve stimulation. Affected individuals show a favorable response to acetylcholinesterase (AChE) inhibitors (summary by Belaya et al., 2012). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Fast-channel congenital myasthenic syndrome (FCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the AChR channel, specifically from abnormally brief opening and activity of the channel, with a rapid decay in endplate current and a failure to reach the threshold for depolarization. Treatment with pyridostigmine or amifampridine may be helpful; quinine, quinidine, and fluoxetine should be avoided (summary by Sine et al., 2003 and Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Slow-channel congenital myasthenic syndrome (SCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the acetylcholine receptor channel, specifically from prolonged opening and activity of the channel, which causes prolonged synaptic currents resulting in a depolarization block. This is associated with calcium overload, which may contribute to subsequent degeneration of the endplate and postsynaptic membrane. Treatment with quinine, quinidine, or fluoxetine may be helpful; acetylcholinesterase inhibitors and amifampridine should be avoided (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Autosomal dominant distal hereditary motor neuronopathy-7 (HMND7) is a neurologic disorder characterized by onset in the second decade of progressive distal muscle wasting and weakness affecting the upper and lower limbs and resulting in walking difficulties and hand grip. There is significant muscle atrophy of the hands and lower limbs. The disorder is associated with vocal cord paresis due to involvement of the tenth cranial nerve (summary by Barwick et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant distal HMN, see HMND1 (182960). [from OMIM]

Congenital myasthenic syndrome-12 is an autosomal recessive neuromuscular disorder characterized by onset of proximal muscle weakness in the first decade. EMG classically shows a decremental response to repeated nerve stimulation. Affected individuals show a favorable response to acetylcholinesterase (AChE) inhibitors (summary by Senderek et al., 2011). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndromes are genetic disorders of the neuromuscular junction (NMJ) that are classified by the site of the transmission defect: presynaptic, synaptic, and postsynaptic. CMS8 is an autosomal recessive disorder characterized by prominent defects of both the pre- and postsynaptic regions. Affected individuals have onset of muscle weakness in early childhood; the severity of the weakness and muscles affected is variable (summary by Maselli et al., 2012). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Slow-channel congenital myasthenic syndrome (SCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the AChR channel, specifically from prolonged opening and activity of the channel, which causes prolonged synaptic currents resulting in a depolarization block. This is associated with calcium overload, which may contribute to subsequent degeneration of the endplate and postsynaptic membrane. Treatment with quinine, quinidine, or fluoxetine may be helpful; acetylcholinesterase inhibitors and amifampridine should be avoided (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome-14 is an autosomal recessive neuromuscular disorder characterized by onset of limb-girdle muscle weakness in early childhood. The disorder is slowly progressive, and some patients may become wheelchair-bound. There is no respiratory or cardiac involvement. Treatment with anticholinesterase medication may be beneficial (summary by Cossins et al., 2013). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome associated with AChR deficiency is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized clinically by early-onset muscle weakness with variable severity. Electrophysiologic studies show low amplitude of the miniature endplate potential (MEPP) and current (MEPC) resulting from deficiency of AChR at the endplate. Treatment with cholinesterase inhibitors or amifampridine may be helpful (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Slow-channel congenital myasthenic syndrome (SCCMS) is a disorder of the postsynaptic neuromuscular junction (NMJ) characterized by early-onset progressive muscle weakness. The disorder results from kinetic abnormalities of the acetylcholine receptor channel, specifically from prolonged opening and activity of the channel, which causes prolonged synaptic currents resulting in a depolarization block. This is associated with calcium overload, which may contribute to subsequent degeneration of the endplate and postsynaptic membrane. Treatment with quinine, quinidine, or fluoxetine may be helpful; cholinesterase inhibitors and amifampridine should be avoided (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome associated with AChR deficiency is a disorder of the postsynaptic neuromuscular junction (NMJ) clinically characterized by early-onset muscle weakness with variable severity. Electrophysiologic studies show low amplitude of the miniature endplate potential (MEPP) and current (MEPC) resulting from deficiency of AChR at the endplate. Patients may show a favorable response to amifampridine (summary by Engel et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome-19 (CMS19) is an autosomal recessive disorder resulting from a defect in the neuromuscular junction, causing generalized muscle weakness, exercise intolerance, and respiratory insufficiency. Patients present with hypotonia, feeding difficulties, and respiratory problems soon after birth, but the severity of the weakness and disease course is variable (summary by Logan et al., 2015). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Congenital myasthenic syndrome-15 is one of a heterogeneous group of disorders that arise from impaired signal transmission at the neuromuscular synapse and are characterized by fatigable muscle weakness (summary by Cossins et al., 2013). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Any congenital myasthenic syndrome in which the cause of the disease is a mutation in the LRP4 gene. [from MONDO]