Clinically, the proband's phenotype was comparable to myotonia permanens, which is characterized by severe myotonia aggravated by cold, onset near birth with possible breathing difficulties, and subcontinuous myotonic EMG.15 Two other SCN4A mutations have been linked to myotonia permanens: G1306E and Q1633E.15,16 Patients with more severe cases may encounter life-threatening severe neonatal episodic laryngospam.16, –, 19 Conversely to her father, the proband did not show clinical manifestation related to myotonic dystrophy except for the orbicularis oculi weakness. The gene discussed is SCN4A; the disease is myotonia permanens.