Congenital myasthenic syndrome (CMS) is an inherited neuromuscular disorder caused by defects of several types at the neuromuscular junction. The effects of the disease are similar to Lambert-Eaton Syndrome and myasthenia gravis, the difference being that CMS is not an autoimmune disorder. There are only 600 known family cases of this disorder and it is estimated that its overall frequency in the human population is 1 in 200,000. Types
The types of CMS are classified into three categories: presynaptic, postsynaptic, and synaptic. Presynaptic symptoms include brief stops in breathing, weakness of the eye, mouth, and throat muscles. These symptoms often result in double vision and difficulty chewing and swallowing. Postsynaptic symptoms in infants include severe muscle weakness, feeding and respiratory problems, and delays in the ability to sit, crawl, and walk. Synaptic symptoms include early childhood feeding and respiratory problems, reduced mobility, curvature of the spine, and weakness, which causes a delay in motor milestones. Presentation
The onset of symptoms for all ages may include droopy eyelids. A particular form of postsynaptic CMS (slow-channel CMS) includes severe weakness beginning in infancy or childhood that progresses to respiratory problems, and leads to loss of mobility in adolescence or later life. Mechanisms
Postsynaptic CMS
CMS is associated with genetic defects that affect proteins of the neuromuscular junction. Postsynaptic defects are the most frequent cause of CMS and often result in abnormalities in the acetylcholine receptor (AChR).
The effect of ephedrine is delayed and the improvement occurs over a period of months.Salbutamol, a selective β(2)-adrenergic receptor agonist, has been found, in adults, to have fewer side effects than Ephedrine and to be more easily obtained in some countries. It has been trialed in children with positive resultsAs of 2022, the standard of care for DOK7  CMS is either ephedrine or salbutamol. People
Two brothers with apparent myasthenic syndrome with a seemingly circadian off/on cycle, living near Quetta, Pakistan were nicknamed the solar kids, because their condition resulted in an inability to move from approximately sunset to sunrise, while their daytime motor abilities were seemingly normal. Doctors observed that some "factor" seemed to become exhausted in the course of normal diurnal activities, and was "recharged" over the period of inertia and sleep. The father first sought help from spiritual healers, then turned to Western medicine. A younger brother of the two had also begun to manifest the same symptoms. The family had other children, two daughters and one son, who were unaffected. The "solar kids" condition, despite extensive testing, was said to be undiagnosed as of 2016, and assumed to be genetic, as their parents were cousins. Samples of their genetic material were to be sent to the UK for analysis. See also
Congenital disorder
Myasthenia gravis
Lambert-Eaton syndrome

References
External links
Congenital Myasthenic Syndromes
About Congenital Myasthenic Syndrome From the Mayo Clinic
Treatment for Congenital Myasthenic Syndromes From the Mayo Clinic