Congenital myopathies and progressive muscular dystrophies . Due to muscle wasting, skeletal deformities result such as kyphoskoliosis causing restrictive ventilatory disorder. Additional problems include weakness of cough reflex leading to obstructive ventilatory problems and cardiomyopathy. Non-dystrophic muscle ion channel disorders. Patients have varying degrees of myopathy and occasionally progressive weakness.
Muscle mass is decreased for the paralyses and increased for the myotonias.
Usually, there is no cardiac involvement, but respiratory muscle may be affected in very severe paralysis attacks. Most of these rare diseases are associated with exercise-induced, electrically silent muscle spasms, muscle pain and myoglobinuria. Particularly, McArdle s disease, a myophosphorylase deficiency syndrome belonging to the group of glycogen storage disorders, may present as intermittent myoglobinuria. Carnitine palmitoyl transferase deficiency type II is a lipid storage disease which can lead to painful muscle spasms and transient muscle weakness potentially followed by myoglobinuria and renal failure. Brody s disease is characterized by painless muscle cramping and exercise-induced impairment of muscle relaxation.