A- Steinert disease:
– Synonym: Myotonic dystrophy
– If transmitted in an autosomal dominant fashion.
– The molecular abnormality in question is located in the gene encoding the protein kinase myotonine (DMPK) on ch.19 by abnormal amplification of a trinuclotidique sequence.
– Atrophy predominant in the cephalic end responsible for a particular facies ptosis, expressionless face and elongated. The voice is nasonnée.
– Muscle disease distal members
– There is often a premature baldness
– Myotonia slowly for relaxation after voluntary movement or after striking a muscle.
– Myotonia in EMG translation feature: myotonic showers
– The systemic disease associated bilateral cataracts, arrhythmias and cardiac conduction, and attacks endocrine (gonadal: sterility)
– Life expectancy rarely exceeds 65.
B- The myotonia congenita Thomsen:
– Autosomal dominant transmission
– The myotonia is aggravated by cold and improved by heat
– Train a real strength of the patient
– This is a chlorine channelopathy.
– Patient has developed muscles
– There is no heart or respiratory disease
– Treatment: carbamazepine, phenytoin. Mexiletine.
2- progressive muscular dystrophies:
A- Duchenne (and Becker):
– Transmission X-linked. Dystrophin absence. C p21 (short arm)
– Manifests around the age of 3 years but walking is acquired before. A difficulty for running, climbing stairs and lumbar lordosis appears and retraction of the Achilles tendon.
– There is a hypertrophy of the muscles of the calves (pseudohypertrophy)
– The child walking on tiptoe and waddling way. Walking becomes impossible at the age of 10 years.
– Other: scapula alata; Gowers sign
– Death occurs around age 20 due to cardiorespiratory failure or decubitus complications.
* The Becker muscular dystrophy Differs clinically by a late start, at the age of 12 years, ranging from 2 to 45 years.The deficit appears to pelvic and shoulder girdle. The distal muscles are preserved. The calf hypertrophy is constant.walking becomes impossible at the age of 30 years and the death occurs around age 40 or cardiac muscle failure.
Dystrophin is abnormal or reduced amount.
* In both pathologies muscle enzymes (CPK) is very high (x10 or x100).
* A mosaic pattern, with positive and negative fibers fibers occurs in female carriers.
B- DUCHENNE LIKE (or girdle muscular dystrophy):
– Autosomal recessive. Fault in the DAG (sarcoglycan).
– Receiving the Maghreb countries because of the frequency of inbreeding
– The signs start between 5 and 12 years; stop walking between 15 and 25 years; death after 50 years (rare heart disease).
C- MYOPATHY OF LANDOUZY-Dejerine (myopathy facial-glenohumeral):
Autosomal dominant inheritance with complete penetrance. Reaching the platysma of the face and facial expression muscles; downward reached; scapula alata very impor aunt …
3- The other myopathy:
* Muscle tissue diseases: McArdle disease (type V) muscle phosphorylase deficiency and disease Tarui (type VII) with phosphofructokinase deficiency.
* Endocrine Myopathy: thyroid dysfunction; hyperparathyroidism; Cushing’s syndrome
* Metabolic myopathy: lipid (carnitine deficiency, carnitine palmitoyl transferase deficiency); mitochondrial myopathy
* Periodic Paralysis: hypokalemic (Westphal’s disease); hyperkalaemic (Gamstorp disease).
+ Disease Westphall (hypokalemia) is linked to a dysfunction of muscle calcium channel (chromosome 1). Favored by the high-carbohydrate meal, cold, emotions … regresses within a few hours (max, 2 to 3 days). Savings facial paralysis and extraocular muscles.
+ Disease Gamstorp (hyperkalemia) is rare; linked to a mutation of the gene (chromosome 17) which encodes the muscle sodium channel. Triggered by fasting glucose, cold, major exercises. Access takes a few minutes to 1 hour.
* Toxic myopathy: myopathy chloroquine is the most characteristic.