Congenital myasthenia is a disease produced by a biochemical defect or a structural alteration of the neuromuscular junction that results in a clinical profile of feebleness and muscular fatigue from birth or early infancy. It is convenient to distinguish these forms of the disease from myasthenia gravis (of autoimmune origin) and the neonatal forms (in children of mothers who have myasthenia gravis).
The prevalence of congenital myasthenic syndromes is estimated to be between 1 in 500,000 (GeneReviews) and 9.2 in 1,000,000 (Parr et al., 2014). Their etiology is genetic in large part. As of today, several implicated genes are known, allowing for up to two thirds of cases to have a positive genetic diagnosis (Jacob et al., 2009).
The genes that are most frequently implicated and their yields are: CHRNE (50%), RAPSN (15-20%), COLQ (10-15%), DOK7 (10-15%), CHAT (5%), and GFPT1 (2%). We have included these six genes as part of the basic study, and we have also developed an extended panel of 29 related genes that will allow optimizing the diagnostic yield.