Duchenne Muscular Dystrophy

1. Duchenne Muscular Dystrophy (DMD)

2. History of DMD It was first described by a french neurologist named Guillaume Benjamin AmandDuchenne in 1868. Previous to the “discovery”, the disorder had been noticed by a Scottish surgeon named Charles Bell, and by an English medical doctor named Edward Meryon. Usually associated with BMD (Becker Muscular Dystrophy), which is a much milder case of muscular dystophy. It is much slower and less predictable. It is usually found in boys, and rarely found in girls “DMD occurs when a particular gene on the X chromosome fails to make the protein dystrophin.”

3. Diagnosis A muscle biopsy (taking a sample of muscle) can be done to test for insufficient amounts of dystrophin. Genetic testing can also be done by taking a blood sample and looking at the genetic code (sequencing) Most tests would include: clinical findings, family history, blood creatinekinase concentration and muscle biopsy with dystrophin studies. These would confirm the diagnosis.

4. Signs and Symptoms Most symptoms usually appear before age 6, and as early as infancy. Delay of maturing milestones such as sitting and standing independently Muscle weakness in arms, legs, neck, and other areas Steady decline of muscle strength Calf muscles will enlarge, and the enlarged muscle tissue will eventually be replaced with with fat and connective tissue (pseudohypertrophy). Muscles are un-usable because the muscle fibers shorten and fibrosis occurs in connective tissue. Usually requires leg braces by the age of 10, and by age 12, a wheel chair is needed. Muscular weakness and skeletal deformities often cause breathing disorders. Cardiomyopathy (enlarged heart) occurs in almost all cases. It is uncommon for an afflicted person to live past 30. Breathing complications and cardiomyopathy usually cause death.

5. Transmition Duchenne muscular dystrophy is inherited in an X-linked recessive pattern. Males have only one copy of the X chromosome from the mother, and one copy of the Y chromosome from the father. If their X chromosome has a DMD gene mutation, they will have Duchenne muscular dystrophy because the Y chromosomes do not have the code to make dystrophin proteins. Because females have two copies of the X chromosome, if one has DMD deficiency, the other one can still may dystophin. Females who carry the changed copy of the gene have a 50 percent chance of passing it on with each pregnancy. Because of this there is a 25 percent chance of having a affected child with DMD.

6. Treatment There is no cure for Duchenne Muscular Dystrophy but the symptoms can be temporarily treated. Steroids can be used to prolong the ability to walk for 2 to 5 years, but side effects can include weight gain, high blood pressure, behavior changes, and delayed growth, so it may not be to the advantage. There are many types of steroids that can be used but they all have varying side effects. Aggressive management of dilated cardiomyopathy with anti-congestive medications is used, including cardiac transplantation if it gets severe.

7. figures Guillaume Benjamin AmandDuchenne Punette square for DMD Affected person

8. Dystophin in muscles (picture)

9. References (NHGRI), N. H. (2009, September 1). Learning About Duchenne Muscular Dystrophy. Retrieved May 18, 2010, from Geome.gov: http://www.genome.gov/19518854#4 Assosiation), M. (. (2010). Facts About Duchenne and Becker Muscular Dystrophies (DMD and BMD). Retrieved May 18, 2010, from MDA.org: http://www.mda.org/publications/ Definition of Duchenne muscular dystrophy. (2002, July 19). Retrieved May 18, 2010, from medicinenet.com: http://www.medterms.com/script/main/art.asp?articlekey=11686 FAQ. (n.d.). Guillaume-Benjamin-AmandDuchenne Biography (1806-1875). Retrieved May 18, 2010, from faqs.org: http://www.faqs.org/health/bios/99/Guillaume-Benjamin-Amand-Duchenne.html