The CX3CR1 antagonist 18a showed similar tendencies to SB 265610 with respect to the viability of RASMCs with and without CMS, and a higher concentration of the CX3CR1 antagonist 18a decreased the viability and increased the death of RASMCs without CMS, consistent with the result that CX3CR1 was expressed in RASMCs without CMS (Fig. 3c and d). The gene discussed is CX3CR1; the disease is congenital myasthenic syndrome.