In the neuromuscular junction there is a vital pathway that maintains synaptic structure and results in the aggregation and localization of AChR on the postsynaptic folds. This pathway consists of agrin, muscle-specific tyrosine kinase (MuSK), acetylcholine receptors (AChRs) and the AChR-clustering protein rapsyn, encoded by the RAPSN gene. The vast majority of mutations causing CMS are found in the AChR subunits and rapsyn genes.Out of all mutations associated with CMS, more than half are mutations in one of the four genes encoding the adult acetylcholine receptor (AChR) subunits. Mutations of the AChR often result in endplate deficiency. Most of the mutations of the AChR are mutations of the CHRNE gene. The CHRNE gene codes for the epsilon subunit of the AChR. Most mutations are autosomal recessive loss-of-function mutations and as a result there is endplate AChR deficiency. CHRNE is associated with changing the kinetic properties of the AChR. One type of mutation of the epsilon subunit of the AChR introduces an Arginine into the binding site at the α/ε subunit interface of the receptor. The addition of a cationic Arg into the anionic environment of the AChR binding site greatly reduces the kinetic properties of the receptor. The result of the newly introduced Arg is a 30-fold reduction of agonist affinity, 75-fold reduction of gating efficiency, and an extremely weakened channel opening probability. This type of mutation results in an extremely fatal form of CMS.Another common underlying mechanism of CMS is the mutation of the rapsyn protein, coded by the RAPSN gene.
Lupoid sycosis is a cutaneous condition that is characterized by a scarring form of deep folliculitis, typically affecting the beard area. See also
Sycosis barbae
List of cutaneous conditions


== References ==