P 1147. Pyridostigmine Leads to Relevant Improvement of Motor Function in an Infant with RYR1-Related Congenital Myopathy

Background: Mutations in the RYR1 gene are associated with a wide range of neuromuscular diseases and one of the most frequent reasons for congenital myopathies. In congenital myopathies, secondary transformations of the neuromuscular transmission with response to acetylchlolinesterase inhibitors are described.

Objective: We report on a 9-month-old female infant with severe muscle weakness, ptosis, and poor feeding suspicious for congenital myasthenic syndrome who was treated with pyridostigmine and showed an obvious clinical improvement. Trio exome sequencing later detected compound heterozygosity for functional relevant variants in the RYR1 gene (c.[(938_940delTCT);(11707C>T)]/p.[(Phe313del)/(Arg3903Trp)]).

Question: Are acetylcholinesterase inhibitors effective in RYR1-related congenital myopathies?

Results: Our patient responded very well to pyridostigmine therapy with noticeable improvement of motor functions and development without any relevant adverse events. Different single case reports in the literature confirm this experience, based on histopathological examinations demonstrating changes of the neuromuscular endplate structure in patients with congenital myopathies.