Follow-up of a family with slow-channel congenital myasthenia syndrome and analysis of the factors of therapeutic efficacy / 中华神经科杂志

ABSTRACT

Objective:To describe clinical characteristics, genetic mutation and therapeutic response of a family diagnosed as slow-channel congenital myasthenia syndrome (SCCMS) and analyze the factors of the efficacy of channel blockers therapy.Methods:Clinical data and therapeutic response in three patients from a family of SCCMS from Department of Neurology, Xuanwu Hospital, Capital Medical University in May 2017 were collected. The clinical data, mutations and response to therapy of all literature SCCMS cases in the English database of Pubmed and Chinese database of Wanfang until December 31, 2018 were analyzed statistically.Results:The proband was a 48-year-old female who referred to Xuanwu Hospital for limb weakness for 40 years. The proband′s elder daughter presented with onset of the birth and delayed motor milestones, scoliosis and difficulty in walking. The younger daughter was born healthy with normal motor milestones, while fatigue and weakness gradually appeared. The antibodies of myasthenia gravis were negative. No repetitive compound muscle action potentials (CMAP) were detected in three patients. Repetitive nerve stimulation showed decrements. Gene test revealed heterozygous mutation of CHRNE p.εV279F, a known pathogenic mutation of SCCMS. Seventeen SCCMS cases were reported in literature. A total of 20 patients with SCCMS were described in terms of clinical manifestation, mutation, drug therapy and efficacy in detail. According to the literature description, they were divided into significant benefit group and mild to modest benefit group to channel blocker therapy. The age of onset in 10 patients with significant benefit was 1.50 (0.75, 28.25) years from birth to 43 years, and that in 10 patients with mild to modest benefit was 2.50 (0, 6.25) years from birth to 11 years. There was no significant difference between the two groups. The age at the initial channel blocker therapy in the group with significant benefit was (23.40±13.29) years from 12 to 43 years, whereas that in the group with mild to modest benefit was (34.10±13.43) years from 20 to 62 years, and there was no significant difference between the two groups. The delay time of treatment (age at the beginning of treatment with channel blockers-age of onset) in patients with significant benefit was 13.0 (10.25, 15.00) years, which was 32.50 (19.25, 38.00) years in patients with mild to modest benefit ( Z=-3.374, P=0.000). According to the response of cholinesterase inhibitor, eight patients were in the effective group, 10 patients were in the ineffective group and two patients were without cholinesterase inhibitor. The age of onset in the effective group was 0 (0, 4.75) years, while that in the ineffective group was 6.50 (1.00, 28.25) years ( Z=-2.315, P=0.021).The age of treatment with channel blockers was (27.90±12.99) years in the effective group and (32.00±13.21) years in the ineffective group, and there was no significant difference between the two groups. The delay time of channel blocker treatment in effective group was (30.25±11.07) years, while that in ineffective group was (14.30±9.60) years ( t=-3.274, P=0.005). Conclusions:In SCCMS, the effect of channel blockers was related to the delay time of treatment. Channel blocker was more effective the sooner it was started after the onset of symptoms. The average age of onset of SCCMS patients with positive responses to cholinesterase inhibitor was younger, but the delay time of channel blocker therapy was longer, resulting in poor therapeutic effect.