Myotonic syndromes Flashcards
subdivided into
dystrophic myotonic syndromes and nondystrophic myotonic syndromes
Nondystrophic myotonic syndromes
are channelopathies and include Thomsen disease AD, Becker disease AR, and Eulenberg disease AD.
manifest with myotonia, muscle stiffness, and weakness. Thomsen disease and Becker disease are furthermore characterized by muscular hypertrophy
Myotonic dystrophies,
one of the most common forms of adult-onset muscular dystrophy.
Both types, myotonic dystrophy type I (DM1, Curschmann-Steinert disease) and myotonic dystrophy type II (DM2, proximal myotonic myopathy), are autosomal dominant conditions with CTG trinucleotide repeat and CCTG tetranucleotide repeat expansions respectively in the DMPK gene → changes in myotonin protein kinase expression
Type I is a severe (often life-threatening) form of disease, while type II is usually mild. Both present with skeletal muscle weakness and myotonia, muscle pain, heart conduction defects, cataracts, testicular atrophy, and frontal balding. Electromyography may confirm myotonia that is not identified during clinical examination;
I:The distal sections of extremities: face, neck, forearm, foot dorsiflexor, intrinsic muscles of the hand.
II:The proximal muscles: neck flexors, hip flexors, elbow flexors, finger flexors
Myotonia
Myotonia: delayed muscle relaxation following normal muscle contraction
Periodic paralysis
A group of rare muscular conditions characterized by recurrent episodes of muscle weakness that typically develop after strenuous exercise, changes in diet, or medication use
-Hypo/hyperkalemic PP
-Thyrotoxic PP
-Andersen-Tawil syndrome
Attacks of focal or generalized flaccid muscle weakness (periodic paralysis)
Proximal muscles are more prominently affected; respiratory and facial muscles are generally spared
Variable duration (hours to days)
Concomitant fatigue, muscle pain, and/or altered state of consciousness during the attacks
