Neurological Disorders: Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is the commonest muscular dystrophy that affects the children.

Muscular dystrophies are nothing but a type of myopathies (muscle diseases) that are hereditary in nature. They are typically progressive in nature although the degree of progression and the prognosis varies considerably from disease to disease.

They can be autosomal dominant, recessive or sex chromosome inked e.g. X linked. DMD is an X linked recessive type of genetic disorder affecting the muscles.

Female gender is the carrier and male gender is the sufferer for this disease. It characteristically presents at a very young childhood (say around age 1).

DMD predominantly affects the skeletal muscles however the cardiac muscle is vulnerable too. Dystrophin is a protein present in the muscle cell wall and provides integrity of the cell wall. Its absence or deficiency is a serious issue as the muscle cell will start degenerating and eventually die.

In DMD there is a mutation (abnormal change) in the gene called as dystrophin gene and it codes for the dystrophin protein. And this gene is located in the X chromosome. In DMD there is total lack of production of dystrophin protein.

Becker’s muscular dystrophy is a less severe form of DMD where there is no total absence of dystrophin production

DMD characteristically starts manifesting from a very early age. Although at birth the child may not manifest with any symptoms, as days pass the delayed motor milestones may be noticeable. Around the age 1 year when the child is trying to stand up it will be invariably noticed. Child will have enormous difficulty in standing up and the standing position will be attempted by a peculiar sequence of movements what is called Gower’s sign (child climbing on itself).

Although eventually child will stand and walk however it is only temporary, as the muscle weakness progresses, child will start regressing or losing the motor milestone. This will continue to progress and around 10 years majority of these patients will become wheelchair dependent.

The disease is not confined to skeletal muscles. Heart muscle may be involved too. A small amount of dystrophin is present in the brain as well so patients may have some intellectual deficiency.

At this time Duchenne Muscular Dystrophy is invariably fatal in nature, although there are few patients who survived well into adulthood but that is not at all the trend. Severe paralysis of the breathing muscles is the main cause for the death although heart diseases might contribute too.

Genetic testing for dystrophin mutation is confirmatory.

Other tests that may be employed include muscle biopsy with routine and special staining, EMG/NCS (electromyography and nerve conduction studies). A blood CPK is invariably done and is elevated.

Lots of researches are going on in the area of gene therapy, stem cell therapy etc and hopefully they find out a cure.

Until that happens we are left with symptomatic and palliative therapy for Duchenne Muscular Dystrophy. Steroids like prednisolone can delay the progression of the muscle degeneration but side effects with chronic therapy is a concern. Physical therapy is employed as long as patient can do it. They generally require wheel chair and other assistive devices around age 10 onwards. Respiratory care is required once respiratory muscle paralysis begins.