Legs and pelvis are affected first in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy and Genetics


When Ranjeetha and Rakesh were preparing Anish, their 3 year old for pre-school, they observed that he had difficulty walking and sitting up. They took a primary treatment from their family doctor but as the problem persisted over the year, they were worried and decided to take him to the specialist and Anish was diagnosed with Duchenna Muscular Deficiency (DMD). They were heartbroken with the thought that Anish would have to spend the rest of his life bedridden, or on a wheelchair – totally dependent on others. But very little they knew that their genes were responsible for his condition.

What is DMD?    

Duchenne Muscular Dystrophy is a disorder caused by inherited mutations in genes. It affects protein in Dystrophin (muscle fibres) and causes progressive muscle weakness because of the breakdown and loss of muscle cells. There are around 20 types of muscular dystrophies, but Duchenne type affects only boys, and in rarest of the rare conditions – some girls. The problem here is, the disease is not diagnosed in the infancy, but around the time when child is around 3-5 years of age.  It is named after gentleman from Paris named Dr Duchenne de Boulogne who worked on DMD for the first time in 19th Century.  Even though inherited faulty genes are linked to this gender-specific disease, it can also affect girls in some rare cases through some mutations.

Curvature in spine due to DMD
Curvature in spine due to DMD

Symptoms

It starts with increasing muscle weakness of pelvis and the area below along with a loss of muscle mass. Slowly the weakness spreads to the other parts of the body. In the initial stage, the symptoms include enlarged calf muscles, low endurance, and difficulty in standing & climbing stairs without any help.

In the later stage, muscle tissue gets replaced by fat and tissues caused by wastage. By age of around 10, the patient requires help for walking and fully dependent by the age of 12-13 years. After that, bones develop abnormally and spine curves in an abnormal manner. Eventually it leads to paralysis. It also affects the intellect of the patient but that is not confirmed.

Inheritance of DMD
Inheritance of DMD

Role of genes

This disorder is caused by an X-linked gene. Here, the carriers of mutated genes are mostly mothers. However, in most of the recent cases, it is observed that gene mutation occurs in the boy himself rather than mother being the carrier. In more than 50 percent of the cases the mother is the carrier of the mutated genes. Son and daughter of the carrier have 1:1 chance of being affected by the mutated genes, but the number of affected girls is very less.

Once a boy in the family has been diagnosed with DMD, it is advised to undergo genetic screening for the other members of the family who may be at a risk of being carriers. At DGL, we have ‘Genetic Testing for Duchenne Muscular Dystrophy which identifies the risk of the disorder and also detects the level of mutations. It helps parents of the affected children to take necessary measures.

The average life expectancy for patients afflicted with DMD is around 25, but this varies from person to person. It’s a disease that affects 1 in about 4000 baby boys. The course of treatment changes according to the stage of the disease. Though there are medications available, physiotherapy plays a major role in comforting the patient and improving their life quality.

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