Facioscapulohumeral Muscular Dystrophy by Emily Greer

Facioscapulohumeral muscular dystrophy is the third most common human myopathy affecting approximately 1 in every 20,000 people. Facioscapulohumeral muscular dystrophy is in most cases an inherited autosomal dominant pattern disease characterized by muscle weakness and wasting (atrophy). Generally, an affected person inherits the deletion from one affected parent, although there are cases where there is no family history those cases are sporadic. This condition gets it’s name from the areas of the body that are most affected: facial muscles (facio), around the shoulder blades (scapulo) and the upper arms (humeral).


The signs and symptoms of facioscapulohumeral muscular dystrophy usually appear in adolescence. However, the onset and severity of the condition varies widely. The muscle weakness associated with facioscapulohumeral muscular dystrophy may worsen slowly over decades and may spread to other parts of the body. Weakness in muscles of the lower leg can lead to a condition known as foot drop, which affects walking and increases the risk of falls. Facioscapulohumeral muscular dystrophy results from a deletion of genetic material from a region of DNA known as D4Z4. This region is located near one end of chromosome 4. The D4Z4 region normally consists of 11 to more than 100 repeated DNA segments, each of which is about 3300 DNA pairs (3.3 Kb) long. However, in people with facioscapulohumeral muscular dystrophy the D4Z4 region on one copy of chromosome 4 is abnormally short, containing between 1-10 repeats.

There are no current treatments for Facioscapulohumeral muscular dystrophy. Recently, there has been some headway made on possible future approaches for treating this form of muscular dystrophy using a disease gene silencing approach called RNA interference (RNAi). RNA interference is a natural cellular process that controls the levels at which certain genes are expressed. In this sense, it operates less like an on/off switch and more like a molecular volume control knob. Over the last several years, many scientists have been working to co-opt these natural gene-silencing strategies for therapeutic purposes. In fact, the main triggers of RNAi in the cell, called inhibitory RNAs or microRNAs, can be designed in the lab to knock down disease genes, such as those genes involved with Facioscapulohumeral muscular dystrophy.

 

References

Lister Hill National Center for Biomedical Communications (2010 May). Facioscapulohumeral muscular dystrophy. Your Guide to Understanding Genetic Conditions. Retrieved Dec. 4, 2011 from Genetics Home Reference database.

Perez, D. “A Possible Approach for Treating FSHD with RNAI Therepeutics.”
FSH Society FSH Watch Research Issue 2011.