MedGen

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 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]

Any abnormality of the neuromuscular junction, which is the synapse between the motor end plate of a motor neuron and the skeletal muscle fibers. [from HPO]

An anomaly in the communication from a neuron to a target across a synapse in the peripheral nervous system. [from HPO]

Syndrome with characteristics of distal, slowly progressive muscular weakness, childhood-onset amyotrophy, autonomic dysfunction characterised by profuse sweating, distal cyanosis related to cold weather, orthostatic hypotension, and oesophageal achalasia. It has been described in two sisters. Inheritance appears to be autosomal recessive. [from SNOMEDCT_US]

Conditions characterized by impaired transmission of impulses at the neuromuscular junction. This may result from disorders that affect receptor function, pre- or postsynaptic membrane function, or acetylcholinesterase activity. The majority of diseases in this category are associated with autoimmune, toxic, or inherited conditions. [from MONDO]

Some individuals have episodes of breathing problems that may be triggered by fevers or infection. Severely affected individuals may also experience short pauses in breathing (apnea) that can lead to a bluish appearance of the skin or lips (cyanosis).

Congenital myasthenic syndrome is a group of conditions characterized by muscle weakness (myasthenia) that worsens with physical exertion. The muscle weakness typically begins in early childhood but can also appear in adolescence or adulthood. Facial muscles, including muscles that control the eyelids, muscles that move the eyes, and muscles used for chewing and swallowing, are most commonly affected. However, any of the muscles used for movement (skeletal muscles) can be affected in this condition. Due to muscle weakness, affected infants may have feeding difficulties. Development of motor skills such as crawling or walking may be delayed. The severity of the myasthenia varies greatly, with some people experiencing minor weakness and others having such severe weakness that they are unable to walk. [from MedlinePlus Genetics]

A rare form of microcephalic primordial dwarfism characterized by a proportionate dwarfism of prenatal onset, a severe microcephaly, a typical dysmorphic face (bird-like), and mild to severe intellectual disability. [from ORDO]

An autosomal anomaly with characteristics of variable clinical features, most commonly including significant intrauterine and postnatal growth retardation, developmental delay, intellectual disability, microcephaly, and dysmorphic facial features. Some less frequent features are cleft lip and/or cleft palate, congenital cardiovascular, gastrointestinal and genitourinary system anomalies. [from SNOMEDCT_US]