Pharmacologic Treatment of Downstream of Tyrosine Kinase 7 Congenital Myasthenic Syndrome

IMPORTANCE Congenital myasthenic syndromes (CMSs) are increasingly recognized as causes of muscle fatigue and weakness. However, treatment of individual syndromes has been described only in small case series. OBJECTIVE To analyze the information published thus far concerning the effect of pharmacologic treatment of one of the most common subtypes of CMS, downstream of tyrosine kinase 7 (DOK7) CMS. EVIDENCE REVIEW In a search of the PubMed database, we found 16 publications describing the response to medication in 122 individuals with DOK7 deficiency. The last search was performed August 15, 2013. If more than 1 article had been published by the same group, a comparison of the participants in the studies was made, and data appearing more than once were excluded. FINDINGS Positive effects were observed in 6 of 66 patients who received an acetylcholinesterase inhibitor, 65 of 69 patients who received ephedrine or salbutamol, 18 of 29 who were given 3,4-diaminopyridine, and 13 of 16 individuals who received a combination of these drugs. Our analysis found no evidence that age at disease onset, age at treatment start, drug dosage, or mutation type influenced treatment results. The magnitude of treatment effect with ephedrine or salbutamol seems to increase gradually, peaking after approximately 6 to 8 months. Treatment with acetylcholinesterase inhibitors resulted in worsened conditions for most patients. CONCLUSIONS AND RELEVANCE This analysis suggests that (1) ephedrine or salbutamol is the first choice of treatment in DOK7 CMS; (2) 3,4-diaminopyridine may provide additional benefi; (3) it is never too late to initiate treatment; and (4) in contrast to acquired myasthenia gravis, treatment with acetylcholinesterase inhibitors should be avoided in DOK7 CMS.