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Distal myopathy
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Distal myopathy

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Distal myopathy
Other names Distal muscular dystrophy
Body Diagram.png
Red depicts the preferentially affected areas in distal myopathy.
Specialty Neurology, neuromuscular medicine
Symptoms Weakness of hands and/or feet
Complications Cardiomyopathy
Usual onset Variable
Duration Lifetime
Types Classic, myofibrillar myopathy, other
Causes Genetic mutation of various genes
Diagnostic method Genetic testing, muscle biopsy
Frequency Rare

Distal myopathy is a group of rare genetic disorders that cause muscle damage and weakness, predominantly in the hands and/or feet. Mutation of many different genes can be causative. Many types involve dysferlin.

Signs and symptoms

All of the different types affect different regions of the extremities and can show up as early as 5 years of age to as late as 50 years old. Distal myopathy has slow progress therefore the patient may not know that they have it until they are in their late 40s or 50s.

Miyoshi myopathy affects the posterior muscles of the lower leg, more so than the anterior muscles of the lower leg.

Cause

DYSF

The cause of this myopathy is very hard to determine because it can be a mutation in any of at least eight genes and not all are known yet. These mutations can be inherited from one parent, autosomal dominant, or from both parents, autosomal recessive. There are eight known types of distal myopathy.

Types

Classic distal muscular dystrophies
Type Eponym Inheritance OMIM Gene Locus Gene also implicated in:
Late adult-onset type 1 Welander AD 604454 TIA1 2p13
Late adult-onset type 2a - Finnish (tibial) Udd AD 600334 TTN 2q31.2
Late adult-onset type 2b Markesbery–Griggs AD ZASP 10q23.2
Early adult-onset type 1 Nonaka AR 605820 GNE 9p13.3
Early adult-onset type 2 Miyoshi AR 254130 DYSF 2p13.3-p13.1 limb-girdle muscular dystrophy type 2B.
Distal myopathy with anterior tibial onset (DMAT) 606768 DMAT can be considered a variant of Miyoshi.
Early adult-onset type 3 Laing (Gower) AD 160500 MYH7 14q11.2
AD = autosomal dominant; AR = autosomal recessive
Myofibrillar myopathies classifiable as distal myopathy
Type Eponym Inheritance OMIM Gene Locus Gene also implicated in:
Desmin — adult onset (MFM1)

Hereditary inclusion-body myositis type 1

AD
αB-crystallin — early - mid adult (MFM2) AD
ZASP— late adult (MFM4) AD
Scapuloperoneal AD
MFM = myofibrillary myopathy; AD = autosomal dominant; AR = autosomal recessive
Other distal muscular dystrophies
Type Eponym Inheritance OMIM Gene Locus Gene also implicated in:
Distal myopathy with vocal cord and pharyngeal weakness AD 606070 MATR3 5q31 Amyotrophic lateral sclerosis 21 (ALS21). One study suggests that all cases are ALS, justifying reclassification.

Diagnosis

In terms of diagnosis, Vocal cord and pharyngeal distal myopathy should be assessed via serum CK levels, as well as muscle biopsy of the individual suspected of being afflicted with this condition

Management

As of 2011, no disease modifying treatments are known. Foot drop can be managed with ankle-foot orthoses or surgical tendon transfer, in which the tibialis posterior muscle is repurposed to function as a tibialis anterior muscle. In select types of distal myopathy, evaluation of the heart may be indicated. Scoliosis and contractures can be surgically managed.

Further reading

External links


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