There have been significant new developments in our recognition of age specific presentations in skeletal muscle channelopathies. A prominent example of this is the phenotype of SNEL: Severe Neonatal Episodic Laryngospasm, a non-dystrophic myotonic disorder due to mutations in the SCN4A gene. SNEL is a striking and alarming disease with infants and very young children experiencing episodic myotonia with a predisposition for respiratory muscles, resulting in respiratory compromise and significant morbidity. Our understanding of the clinical presentations of these SCN4A mutations, their variable severity and intriguingly their evolving phenotype with age beyond two years seeing a dramatic reduction in respiratory symptoms, continues to grow. Exactly why clinical symptoms change with age however remains incompletely understood.

At the opposite end of the age spectrum episodic symptoms in periodic paralysis also appear to decline in severity in older patients often giving way to myopathy. New methods to study in vivo channel function have indicated that normal ageing alters ion channel activity contributing to this change in phenotype.

Age has long been a critical determinant in myotonic dystrophy with distinct challenges and needs arising from congenital onset, childhood onset and adult onset presentations. Delay to diagnosis and awareness of the condition continues to be a major problem with many congenitally affected infants born to undiagnosed, although usually not asymptomatic mothers. Improved access, reduced costs and speed of genetic analysis has not been matched with improved disease recognition. Promoting diagnosis and clinician awareness is an urgent unmet need.

Sex differences are noted in hypokalaemic periodic paralysis and myotonia congenita. They are also described in DM1 and 2 with emerging evidence that this may influence response to disease modifying treatments. This is an under-explored area especially in myotonic dystrophy.

We propose a special edition that will invite experts to discuss these age and sex differences and to submit new data that may yield new insights.

Dr. Giovanni Meola is a consultant in the Scientific advisory Board of Lupin.

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Frontiers in Neurology

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