Motor endplate remodeling in some cases with congenital myasthenic syndrome

The architecture of motor endplates in three cases with congenital myasthenic syndrome (CMS) was compared with ultrastructure of the normal control neuromuscular junction (NMJ). The remodeling of postsynaptic region was observed in all three individuals. The most conspicuous abnormalities seen in the slow channel syndrome was the vacuolization and disorganization of secondary synaptic clefts which extended for beyoned the border of NMJ. Degenerated postsynaptic nuclei and junctional sarcoplasm were an additional feature of presented syndromes. The quite different feature of NMJ was observed in the DOK-7 deficient syndrome. The appearance of small, pale terminal axons, poorly developed postsynaptic membrane with the sparse secondary synaptic clefts and degenerated postsynaptic nuclei suggested impairment of postsynaptic region maturation. The conjunction of postsynaptic membrane paucity and its degeneration was a specific structural feature observed in the third syndrome with no established genetic defects.