• Register
  • Login
  • Bookmark this page!
Skip Navigation LinksHome Page    >    The various genetic diseases    >    Facioscapulohumeral muscular dystrophy (FSHD)
 
 
Pregnancy links...
Health links...
Genetics links...
Medical links...
Autism links...
Other links...
 

Facioscapulohumeral muscular dystrophy (FSHD)


Types and clinical signs

This is one of the more common diseases in the group of muscular dystrophies, and is second in frequency to Duchenne muscular dystrophy.

The muscle weakness usually starts in the muscles of facial expression. The weakness progresses and usually by adolescence the facial expression appears frozen, like a mask, and the patient has difficulty in closing his eyelids and in moving his lips while laughing. The disease also spreads to other parts of the body, mainly the shoulders. The patient then has difficulty in lifting his shoulders and the scapula (shoulder blade) becomes fixed. Sometimes the disease progresses more quickly and sometimes more slowly. A precise diagnosis is important, and a diagnosis made in the past is not always accurate by today's standards. Because of this, the diagnosis must always be confirmed in a genetic institute by examining the patient, or at least by reviewing the results of neurological tests, laboratory and/or EMG results, and other data. Even though we know a lot about the inheritance patterns, the risk of recurrence, pathogenesis, etc., most of these diseases have exceptions, and each case/family must be examined individually in a genetic institute.

Inheritance pattern

Autosomal dominant inheritance.

Penetrance

The expression of the disease is usually full. There is great variation in the severity of the disease; some patients have very few problems. In contrast, in others the muscle weakness can be marked to the point of severe disability.

Associated features that can be demonstrated in tests performed during pregnancy

There are no specific signs in pregnancy.

In families in which the mutation that causes FSHD is present, a reliable genetic test can be performed in the fetus if there is a high risk that he or she may be affected.

The disease cannot be detected by ultrasound examination in pregnancy.

It is important to bring to genetic counseling all available data including the results of any additional tests carried out during pregnancy such as alpha-fetoprotein, nuchal translucency, etc.

What is the risk of recurrence in a subsequent pregnancy?

Each patient has a 50% risk of having a child with the same condition. In a family with FSHD, even asymptomatic individuals may develop the disease at a later age. This means that healthy family members are also at risk of having affected children. In families in which the characteristic gene for FSHD has been found, all the carriers can be identified, even if signs of the disease have not yet appeared.

The exact risk for more distant relatives depends on the number of affected individuals in the family, the relationship of each to the patients, consanguinity between the parents, if any, etc. The risk is ascertained within genetic counseling.

Molecular genetic information

The gene for the disease and the location of the gene

The mutation is a deletion in a relatively small segment at the end of chromosome 4, in a region known as 4Z4D. The characteristic of this region is that normally there are multiple repeats of this segment - it is common to find regions that are repeated a large number of times at the ends of the chromosomes. In FSHD, there is a decrease in the number of repeats to less than 10 (normally there are 10 to 100 repeats). The deletion of a number of repeats can be demonstrated in FSHD using molecular genetic methods.

Genetic testing

Diagnostic testing

When a patient presents with clinical FSHD, a direct test can be performed in order to look for the common mutation that is present in most patients (the deletion of the specific segment in chromosome 4). See: Testing the disease-causing gene for mutations that are common in a specific ethnic group - autosomal dominant diseases.

Carrier testing

The carriers are actually patients, even if they have not yet developed any signs of the disease. In families in whom the specific mutation has been found, relatives carrying the gene can be examined. Tests to identify carrier status in the healthy population are currently not carried out.

Fetal testing

As for diagnostic testing.
 
Haven't found what you're looking for? Search for it here:   
Comments (0)





Leave a Comment
Name
Email (will not be published)
Website (optional)
Subject
Your Comment

Line and paragraph breaks are automatic.

Please type the characters you see in the picture:


All content Copyright © 2009-2011, Genetics of Pregnancy Encyclopedia Corporation. All rights reserved.