Duschenne muscular dystrophy 
– a disorder resulting from mutation of dystrophin gene 
– signs + sx: weakness of lower limbs first and pseudohypertrophy or calf muscles (Gower’s sign = pt “walk” on their hands and arms up their body to get to a standing position due to lack of strength in their hip and thigh muscles) 

 

Myotonic Dystrophy 
– Signs + sx: pt presents with myotonia and weakness of face, neck, and intrinsic hand muscles 
– Due to mutation of DMPK gene 

 

Central Core Disease 
– Signs + sx: neonatal hypotonia and weakness
– Mutation in RYR1 gene 

 

Hypokalemic periodic paralysis 
– Signs + sx: episodes of weakness that lasts hours to days and is triggered by exercise, large carbohydrate meals, salt, insulin, and steroids 
– Can be due to mutation in CACNA1S gene