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Skip Navigation LinksHome Page    >    The various genetic diseases    >    Inclusion body muscular dystrophy (HIBM)
 
 
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Inclusion body muscular dystrophy (HIBM)


This is a type of progressive muscular weakness accompanied by the appearance of typical microscopic changes in the muscle (inclusion bodies). The muscle weakness starts in the lower limbs. Typically, the muscles at the front of the thighs remain unaffected despite the severe weakness of other muscles in the legs. The weakness then progresses to the upper limb muscles also, and eventually it progresses to severe, diffuse muscle weakness. The disease is common in Israel among Jews of Persian, Afghani, Egyptian and Iraqi origin. The muscle weakness usually starts at around the age of 20 years and its rate of progression varies from case to case. In cases where either of the partners is of Iranian, Iraqi, Egyptian or Afghani origin, a test for carrier status for inclusion body muscular dystrophy is advisable.

Penetrance

The penetrance is full and the disease is usually fully expressed.

Inheritance pattern

Autosomal recessive.

What is the genetic defect?

The defect here is in the gene called GNE.

This type of HIBM is important in Jews of Iranian origin because they have a unique, common mutation.

This is M712T?C, where the base T (thiamine) is replaced by the base C (cytosine) in exon 12 of the gene.

This causes the amino acid methionine to be replaced by threonine in position 721 in the protein created by the GNE gene.

The frequency of carriers of this mutation in people of Persian origin in Israel has been found to be relatively high, at up to 1 in 10 of the normal healthy population.

In Jews of Iranian, Iraqi and Afghani origin a direct test can be carried out to look for the specific mutation. Similarly, carriers of the defective gene can also be identified. See: Seeking common mutations responsible for a disease in an ethnic group - autosomal recessive disease

What is the risk of an affected child when both parents are carriers?

The risk is 25% in every pregnancy. Other family members do not have a high risk (usually less than 1%); this can be determined with genetic counseling for each person individually according to their pedigree.

Are there prenatal tests that can test for this disease?

In families in which both partners have been found to be carriers and where the precise genetic defect has been defined, a specific, reliable genetic test can be performed on amniotic fluid cells or chorionic villi.
 
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