Miyoshi myopathy (Miyoshi muscular dystrophy, MMD1) was first described by Prof.
Kazuo Miyoshi the late honorary professor of Tokushima University) in 1967.
Miyoshi myopathy is an autosomal recessive muscular disease. In 1998, it was reported that Miyoshi myopathy was
caused by mutations in the dysferin gene (DYSF) at chromosome 2p13, and the gene product was named dysferlin.
Deficiency of dysferlin causes attenuated sarcolemmal repair and results in muscle atrophy and weakness.
In general, this disease is called Miyoshi muscular dystrophy, Miyoshi distal muscular dystrophy and Miyoshi myopathy.
distal muscular dystrophy : MDMD
Miyoshi muscular dystrophy : MMD1
Miyoshi myopathy : MM
The Miyoshi myopathy with early-adult onset is characterized by the primary involvement of distal muscles.
At an early stage, the patient cannot stand on their tiptoes or jump, tumbles down on a flat road while walking,
and has difficulty going up and down stairs.Patients will be wheelchair-bound within 10 years from onset. Because the
cardiac or respiratory system is not affected in dysferlinopathy patients, the prognosis of dysferlinopathy is
relatively better than other muscular diseases.
You may be diagnosed as one with a hepatic dysfunction because the value of creatine kinase (CK) in the serum
is 10-folds higher than normal (5000-20000 IU/L) on clinical examination of blood. This high CK value is a strong
indication of muscular dystrophy.
In addition, you may have an electrocardiogram, lung capacity test, CT, MRI, electromyography, muscle biopsy
and bone density inspection.Histopathological examination of muscle will reveal dystrophic change
(atrophy and regeneration of myofiber, the increase of connective tissue), and immunohistochemical analysis using
anti-dysferlin antibody can definitively diagnose one with dysferlinopathy because dysferlin is
deficient in the patient’s sarcolemma. Muscle biopsy of the arm or leg will be performed once to confirm the diagnosis.
Mutations in the dysferlin gene also cause limb-girdle muscular dystrophy (LGMD2B).
Dysferlinopathy is the generic name of a muscular dystrophy caused by mutations in the dysferlin gene.
Muscular disease is a disorder involving muscle atrophy and is classified
as myogenic or neurogenic.
Myogenic muscular atrophy results from the problem of muscle itself and causes loss of muscle mass,
while neurogenic muscular atrophy is caused by the nerve problem.
CK (creatin kinase) is an enzyme in cardiac and muscle cells, and its normal value is approximately 35-210.
Patients with muscular disease exhibit very high CK value, more than 10-times that of healthy individuals.
Healthy individuals show a high CK value after exercise, however it is much lower than a patients’ CK value.
The CK value indicates the degradation of skeletal muscle and varies in disease and/or the individual.
[Autosomal recessive inheritance]
A child inheriting mutated genes froｍ parents will develop the disease, and a child inheriting a normal gene and
mutated gene will not develop the disease.
[Distal muscular dystrophy]
Distal muscular dystrophies are characterized by primary involvement of distal muscles, finger and/or lower leg.
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