The near site mutation, Ala1156Thr, was presented in a family with variable features of hyperPP and PMC, and Ile1160Val resulted in potassium-aggravated paramyotonia.[3] The patients in this study were characterized of facial stiffness, eye closure myotonia, and serious limbs' stiffness supporting the diagnosis of MC.
Sodium channel mutations in acetazolamide-responsive myotonia congenita, paramyotonia congenita, and hyperkalemic periodic paralysis.
In paramyotonia congenita, mutations in the muscle sodium channel gene prolong the channel's opening, causing higher-than-normal muscle excitation.
Symptoms: Paramyotonia congenita causes episodes of muscle stiffness and weakness -- mostly in the face, neck, and upper extremities -- that can last from minutes to hours.
Also, a doctor might test for periodic paralysis by having the patient consume safe doses of carbohydrate or potassium, or for paramyotonia congenita by immersing the patient's arm in cold water.
What are myotonia congenita and paramyotonia congenita?
Myotonia congenita and paramyotonia congenita were first described in the 19th century and are nonlethal and generally nonprogressive diseases of voluntary muscle.