Familial Normokalemic Periodic Paralysis Associated With Mutation in the SCN4A p.M1592V

Chao Fu,Jia Li,Xiaoyang Liu,Jiajun Chen,Ling Qi,Zhenyu Wang,Qiuling Sang,Hui Jin,Libo Wang

doi:10.3389/fneur.2018.00430

Abstract

Periodic paralysis (PP) is an uncommon inherited disorder causing recurrent episodes of muscle weakness, with an incidence of 0.001%. Normokalemic periodic paralysis (NormoKPP) as the rarest subtype of PP contains both familial and sporadic. Familial NormoKPP caused by the p.M1592V mutation of the skeletal muscle sodium channel alpha subunit (SCN4A) gene is rarely reported. Only three pedigrees of NormoKPP related to mutations in the SCN4A p.M1592V have been previously reported. We herein presented a family case of NormoKPP associated with the SCN4A p.M1592V mutation, in which respiratory muscle paralysis occurred in the proband while not in his children. Moreover, we conducted a thorough literature review. To our knowledge, this is the first report of respiratory muscle paralysis as a symptom of NormoKPP associated with mutation in the SCN4A p.M1592V.

Highlights

Periodic paralysis (PP) is a rare muscle disease characterized by recurrent muscle weakness, occurring at a rate of 0.001% [1]
Routine laboratory tests found elevated fasting glucose (17.98 mmol/L, normal reference range
Only three families of NormoKPP induced by the p.M1592V mutation have been reported in the literature (Table 2)

Summary

INTRODUCTION

Periodic paralysis (PP) is a rare muscle disease characterized by recurrent muscle weakness, occurring at a rate of 0.001% [1]. We report a familial NormoKPP associated with the SCN4A p.M1592V mutation, and reviewed the literature. First limb flaccid paralysis occurred at the age of 4, lasting for 5–13 days During this episode, his muscular strength could barely lift his limbs from the bed (3/5), while his proximal limbs were even weaker (2/5). Large dosage of normal saline could relief the symptoms during the attack, and they was administrated with 250 mg of acetazolamide twice a day during intermittent period. They refused to do the neurophysiological test. The mutation resulted in a change from methionine to valine (p.M1592V) (Figure 2A) His children had the same heterozygous mutation point in the exon region of the SCN4A gene (Figures 2B,C).

DISCUSSION

Findings

ETHICS STATEMENT