Muscular dystrophy, how it affects ?

Muscular dystrophy

Muscular dystrophy is a group of hereditary diseases that affect the musculoskeletal system. As a result, it affects limb movement due to weakening of the muscles. Muscular dystrophy is characterized by progressive muscle weakness due to death of muscle tissue cells. The weakening may also occur as a result of defects in the muscle proteins.
Muscular dystrophy can be defined as a group of hereditary diseases with progressive degeneration and weakness of a specific group of muscles. Dystrophy actually means wasting away of a particular part, organ or tissue. So muscular dystrophy involves wasting of muscles due to slight alterations in the genetic makeup. The genes contain altered information about the muscles. These dystrophies are slow in onset and usually start showing by early childhood. The primary abnormality may be in the muscle membrane. But secondary effects are marked variation in size of individual muscle fiber. The effect also includes deposition of fat and connective tissue. Muscular Dystrophy is very rare in occurrence. People with this disorder tend to have restriction of movements and sooner or later, require a wheelchair.
The Muscular dystrophy definition covers a wide variety of dystrophies which vary due to different genes being affected.
Depending on the gene involved, the symptoms and age of presentation may vary slightly.
Duchene muscular dystrophy (DMD) is the commonest and is mostly limited to boys and presents itself between 2- 6 years of age.
There is gradual weakening of muscles of hips, arms and legs due to which they are unable to walk, run and climb stairs. Survival beyond 20 years is rare in this dystrophy.

In the year 1860, French neurologist Guillean Duchenne, described an illness in 13 boys who suffered progressive muscle weakness. These boys were unable to walk later. Most of them died. He described the disease in several forms, based on the symptoms and the causes

The types of muscular dystrophies are different and may vary in severity of the symptoms. Duchenne and Becker muscular dystrophies occur as a result of genetic mutations on the x chromosome.

Clinical manifestations for muscular Dystrophy ranges from disorders of the limbs to other organs. Following is the list of organs that can show the manifestation of Muscular dystrophy

  • Eyes
  • Face
  • Limbs
  • Gastrointestinal system
  • Endocrine glands
  • Nervous system
  • Heart
  • Brain

Muscle dystrophy symptoms

The symptoms of Muscular dystrophy vary but the basic symptoms remain more or less the same. The important trait of increasing weakness of muscles is a constant feature in all the types of muscular dystrophies. Other symptoms include difficulty in co-ordination and balance while walking. This leads to frequent falling. Muscle exhaustion and weakness are hallmark symptoms. As a muscle is attached to a joint, it leads to joint stiffness and immobility. Muscles of the chest and throat are also involved which results in difficulty in breathing and swallowing. As the disease progresses, muscles of various parts of the body get involved and ultimately organs too get affected. The progression and severity of symptoms differ from patient to patient.

Muscular dystrophy diagnosis

Muscle biopsy and an electromyogram (EMG) are done to diagnose the condition. Many genetic disorders can be detected by D.N.A analysis and a muscle biopsy nowadays is reserved when genetic tests are not conclusive.

Diagnosis of muscular dystrophy in a child is normally done through testing for the levels of an enzyme called creatinine kinase in the blood. Children with muscular dystrophy tend to have very high levels of this enzyme. Further diagnostic tests may include DNA testing to look out for genetic mutations. Muscle biopsies have also been done as a confirmation. In many cases, it is the overt symptoms such as loss of muscle mass that may prompt health care professionals to do a laboratory diagnosis.

Progressive Muscular dystrophy

Progressive muscular dystrophy, showing the enlargement of the calves and the atrophy of the shoulder muscles. Progressive muscular dystrophy, facio-scapulo-humeral type.

Muscular dystrophy treatment

There is currently no cure for muscular dystrophy but patients who get help early in life have a higher chance of survival and living a more fulfilling life. There are a variety of services d for patients with muscular dystrophies. Treatment options for muscular dystrophy vary depending on the symptoms manifested. Physical therapy is important. It helps a child with muscular dystrophy to maintain muscle tone and muscle strength. It is important to keep the joints flexible. Certain devices e.g. braces may be used to prevent contractures and stiffening of the muscles. Steroid prescriptions, in particular, prednisone, have been used over the years. These are believed to slow down the rate of muscle deterioration. The aim is to enable the children to be able to walk longer and live a more active life. The side effects that come along with prednisone should be closely monitored. Patients with severe muscular dystrophy may also undergo spinal fusion. This is a type of surgery which is aimed at reducing pain and lessening the severity of the spinal cord curvature. It helps the patient to sit upright and comfortably. Additional treatments include good health care and updated vaccinations.

Unfortunately, there is no cure for this condition other than supervised physical therapy and exercise which aims at improving the quality of life as well as course of the disease. Genetic counseling is very important for couples to analyze the risk of the child inheriting this condition.

As the Muscular Dystrophy definition implies, there is muscle breakdown over a course of time. The treatment cannot reverse it yet. The prognosis is poor as respiratory and other vital muscle groups get damaged leading to a life of dependency over time.

Being a genetic condition, not much can be done to prevent muscular dystrophy. Recently, a lot of research and awareness has started. Many families with children suffering from muscular dystrophy are able to get help in terms of treatment and relevant information.

Another common muscular dystrophy is Becker Muscular Dystrophy. (BMD) is very similar to Duchene Muscular Dystrophy except that it occurs usually in adolescence and adulthood with slower degeneration of muscles.

Is muscular dystrophy contagious?

A muscular dystrophy is not contagious or infectious. It is acquired from parents right from birth. It is a genetic disorder in which some genes that contain information regarding muscles are altered. Different muscular dystrophies have different genetic alterations or mutations. Hence, they show slight variation in presentation of symptoms. Most important being that the proteins of the muscles are not produced or if produced do not perform their functions completely. These proteins are required for maintaining the strength and function of muscle fibers. As a result, wasting and degeneration occurs which results in ultimate death of the muscle fibers.

MDA.org provides good support information for muscular dystrophy patients.

Other good resource for reading is US National Library of Medicine

Muscular dystrophy causes

The main cause of muscular dystrophy is genetic defect of Dystrophin protein complex.
Muscular dystrophy is hereditary in nature and passed on in the family.
Dystrophin, a protein, is normally present in the muscle fibers. This protein is deficient or absent in patients having a muscular dystrophy. There is genetic mutation of the dystrophin gene which causes muscular weakness leading to multiple problems in locomotion.
The main cause of Duchenne Muscular dystrophy (DMD) an X chromosome linked disorder is the impaired formation of the protein dystrophin by the muscle tissue.

DMD is generally seen only in boys and is very characteristic since it is X linked. Becker Muscular Dystrophy (BMD) like Duchenne affects only boys but the variation is that there are partially complete forms of dystrophin protein seen in the muscles.

Myotonic muscular dystrophy is another variant in which the cause is autosomal dominant linkage. i.e. the autosomal type of chromosomes in the cells are affected. It is passed on to 50 % of the offspring.

Congenital muscular dystrophy could be caused by multiple gene linkages and hence very dangerous and rare.

The dystrophin protein is necessary for the movement of muscles and since this protein is lacking there is manifestation of the various symptoms.

A deeper understanding of the muscular dystrophy causes will help us understand how a patient presents with progressive muscular weakness which travels from the upper part of the body and then goes lower down. This weakness leads to difficulty in walking and limits mobility. Patients prefer to be static in one place. Even if they walk, they tend to fall often. This leads to bruising of joints and a waddling (penguin-like) gait.

Contractures of tendons leads to stiffness of joints. This is a common finding in this disorder. There is enlargement of calf muscles to help compensate for the inherent weakness but in reality the muscles are wasted. Extreme cases will display difficulty in breathing, drooping of eyelids and spasms of muscles. Difficulty in speaking and later, breathing often lead to becoming bedridden.

Drooping eyelids in muscular dystrophy Drooping eyelids in muscular dystrophy
Cumulus at nl.wikipedia [GFDL or CC-BY-SA-3.0], from Wikimedia Commons

Weakening of chest and back muscles could cause the spine to have a curve. This condition is called as Scoliosis. Scoliosis (abnormal sideways bending) of the spine leads to lack of appropriate posture habits.

Scoliosis due to weak chest and back muscles Scoliosis due to weak chest and back muscles.By Weiss HR CC-BY-2.0 via Wikimedia Commons

Gower’s sign is a very important diagnostic sign which helps in differentiating muscular dystrophy from other conditions. In Gower’s sign, the person finds it difficult to get up from sitting position and hence first raises the thighs and the hip such that the person is half bent over and then by putting all the pressure over the knees, pushes himself over the floor. It appears that the patient is ‘climbing over himself’.

Gower's sign important feature of Muscular dystrophy

A grasp of the muscular dystrophy causes have laid down the foundation for better treatment of the condition. Medical treatment of this disease has been tried with various drugs but prednisone (steroid) has shown the best results. A low dose of prednisone will palliate the symptoms initially.But later there tends to be complications due to long term therapy with prednisone. Creatine monohydrate supplementation has shown slight increase in muscle use and also in reduction of the weakness to some extent. Surgical therapy comes in the picture when there is severe weakness along with deformities. Orthopedic correction comes into play to correct the deformities of the foot and the contractures of joints. The foot deformities start off early and the joint deformities come at a later age. Scoliosis needs to be corrected with braces and a belt, as it is seen early in life and keeps progressing.

So it is important to note that Muscular dystrophy causes do not include the following-

  • Infection of any form from other patients.
  • Infection from Bacteria or virus
  • Any food or nutrients related deficiency
  • Lack of exercise or disuse of muscles

Is muscular dystrophy hereditary ?

Yes, Muscular Dystrophy is hereditary.
Muscular dystrophy is a group of chronic hereditary diseases characterized by progressive degeneration and weakening of muscles. As a result, the musculoskeletal system weakens and hinders the body movement.
It is believed that muscular dystrophy is more of a childhood disease. However the clinical onset may occur at any point in life. Different types of muscular dystrophy vary in age of onset, degree of muscle wasting and the groups of muscles affected.
Muscular dystrophy is certainly hereditary. This means that there is a genetic link to the cause of this disease. It comes about as a result of changes(mutations) in the genes that are responsible for structure and function of one’s muscles. These mutations cause changes in muscle fibers.
Muscles are made up of group of cells called fibers which appear in bundles. On the membranes surrounding these fibers are a group of proteins that aid in the functioning of the muscles. This happens mainly because of the largest gene called Dystrophin in humany body. This may be either absent, defective or partially present in cases of Muscular Dystrophy.
The changes(mutations) in muscle fibers are often inherited and hence the different Muscular Dsytrophy types follow different inheritance patterns. The genetic defect may be transmitted by one parent in some conditions and by both parents in others. However many cases are even seen for muscular dystrophy in families with no history of the disease. This is believed to be a result of a highly spontaneous mutation rate. The mutation may have existed in the family without being known or a new genetic mutation may actually take place in the mother’s eggs cells
Duchenne Muscular Dystrophy is inherited in a x-linked pattern since the gene that carries the mutation is on the X chromosome.

Is Muscular Dystrophy hereditary?

Muscular Dystrophy is hereditary. [P.D]-Wikimedia Commons

 

How is Duchenne muscular dystrophy hereditary ?

An example of the genetic inheritance link for Duchenne muscular dystrophy is seen above .Based on the diagram, males have an XY chromosome while females have XX chromosome. Every boy inherits an X chromosome from the mother and a Y chromosome from his father. A girl gets one X chromosome from the mother and another X chromosome from the father.
When a boy is born to a woman with a Dystrophin mutation on one of her X chromosomes, he has a 50% chance of inheriting the gene and suffering from muscular dystrophy. Each of the daughters belonging to this woman have a 50% chance of also inheriting the mutation and being carriers. A carrier does not have any disease symptoms, but their child can be born with the mutation.
A male with Muscular dystrophy is unable to pass the flawed gene to his sons because he gives the Y chromosome and not an X. But he will certainly pass it to his daughters since girls inherit their father’s only X chromosome. They then become carriers and each of their sons develops a 50% chance of developing the disease and so on.

 

Girls usually do not get muscular dystrophy because when they inherit the flawed Dystrophin gene, they also get a healthy Dystrophin gene from the other parent and thus end up having enough Dystrophin to protect them from suffering from the disease. Boys who inherit the flawed gene get the disease because of lack of a second Dystrophin gene to make up for the faulty one.

REFERENCES

1. 1: Emery AE. The muscular dystrophies. Lancet. 2002 Feb 23;359(9307):687-95.Review. PubMed PMID: 11879882.

2. 1: Hsu YD. Muscular dystrophy: from pathogenesis to strategy. Acta Neurol Taiwan.2004 Jun;13(2):50-8. Review. PubMed PMID: 15478675.
3. http://www.mda.org.au/Disorders/Overview.asp
4. http://www.muscular-dystrophy.org/about_muscular_dystrophy/conditions

Muscular dystrophy Types

There are nine main types of Muscular dystrophy.
These are Becker, Facioscapulohumeral, Myotonic, Distal, Duchenne, Emily-Dreifuss, Limb Girdle, Oculopharyngeal, and Congenital Muscular Dystrophy.
But there are also some conditions that mimic muscular dystrophy and cause the same symptoms. Therefore extensive tests and investigations need to be done before coming to a conclusion of Muscular Dystrophy.

Duchenne Muscular Dystrophy

This is unfortunately the major life claimer of all the Nine Muscular Dystrophy types. It affects only boys. It usually shows up in toddlers. By the time child reaches teenage, he might be severely crippled. DMD is caused by the absence of a gene called Dystrophin. Severity of condition is directly proportional to the amount of Dystrophin absent. The lesser dystrophin a child has in his DNA, the lesser is his chances of surviving beyond adulthood.

What to expect as regards life span of Muscular dystrophy ?

Muscular Dystrophy type 2: Facioscapulohumeral Muscular Dystrophy (FSHMD, FSHD or FSH)

This Muscular Dystrophy type affects both males and females almost equally. As the name suggests, muscles of the face, shoulders and upper limbs are the first ones to be weakened. The prognosis is not that great, and it has been proved that the majority of affected population is in its teens . It leads to severe disability and failure of respiratory system, that may often cause death.

  • Weakness in muscle of face. This results ins drooping of eyelids poor expression of face and difficulty in pronouncing certain alphabets.
  • Heart beat/ rhythm is irregular.
  • Shoulders become weak. The patient cannot raise shoulders, they tend to droop.
  • Patient is unable to hear properly.
  • Sometimes even foot drop is seen in such cases.
  • Muscles of abdomen, lower arm, triceps, biceps and deltoids are weak.

 

Myotonic Muscular dystrophy

This condition is of two types, both of which present with Myotonia or a delayed muscle response specially when relaxing the muscle after contracting. Visualize it this way, the person can pick up a glass full of water, but his muscles would resist keeping the glass down swiftly, causing a much delayed and sometimes-painful reaction. Type 1 Myotonic Muscular dystrophy type is the most common of all such dystrophies and is caused due to repetition of an essential muscle protein twice in the DNA. On the other hand, the type 2 is much rarer and is caused when one muscle protein is expanded beyond its usual size in the Human DNA.

Emily-Dreifuss Muscular Dystrophy

The common population affected by this Muscular dystrophy type is often children or young toddlers. It has three subtypes that dictate the prognosis of the condition, but all have some or more mutations or defects in the EMD gene. Children often exhibit cardiac conditions along with muscular dystrophy like valve defects and arrhythmia. The cause of this change in gene structure remains unknown.

Congenital Muscular Dystrophy

This Muscular dystrophy type is one that is reported at birth itself. Or it may show up to an age of one year. The life span of the child is greatly reduced. The weakness starts from the legs and soon enough, takes over all the body. Sometimes the child may also exhibit neurological problems such as memory difficulties and lower IQ levels. These are also caused by defective muscle protein that is important in formation of Glycoprotein- dystrophin complex. This complex is essential for muscle health.

Limb girdle Muscular Dystrophy

This type of Muscular dystrophy covers a vast subgroup. It has many conditions as subtypes, but most of them exhibit the same symptoms of muscle weakness and progressive deformities in the legs. Usually both girls and boys are equally affected. This shows up mostly in the teenage years. Death is often associated in case complications from heart or respiratory system arise.

Oculopharyngeal Muscular Dystrophy

As the name suggests, the muscles of the eye, throat and face are the first ones to get affected in this Muscular dystrophy. The usual affected population is between 40 to 80 years. It is caused by the repetition and expansion of one gene in the otherwise normal chromosomal structure.

Becker’s Muscular dystrophy

This is a form of muscular weakness, which is considered less severe than other forms of Muscular dystrophy types. It affects only males. It exhibits formation of a distorted dystrophin gene that is slightly functional, unlike other conditions where there is no formation of dystrophin. The patients can survive up to old age after prompt diagnosis. Becker’s Dystrophy has a better prognosis than most of others.

Distal Muscular Dystrophy

This is the least life threatening of all Muscular dystrophy types. The usual affected population can be anywhere between 20-60 years of age. The wasting of upper limb muscles as well as small muscles of the foot is common. The cause of this muscular dystrophy is a defective gene. Thisis the same gene that is involved in Limb Girdle Dystrophy.

Muscular dystrophy life expectancy

Related image

Muscular dystrophy life expectancy is an very important aspect that the patient and their families need to understand and cope up with.
Almost 50,000 people are affected by Muscular dystrophy of one or the other type in US today.
Muscular dystrophy is a disease comprising of almost 20 different genetic disorders. This disease is seen more in males than females. It has no specific tendency towards race or ethnicity. However, the life expectancy completely depends on the condition, as well as the age at the time of diagnosis. In this disease, muscles are destroyed over a period.
The only unifying symptom of all forms of muscular dystrophy is the fact that over time, muscles degenerate and start atrophying. The people, mostly children, suffering from this disease cannot escape the muscle deterioration. This is one fact that those affected need to face. The life expectancy is totally dependent on the type of Muscular dystrophy and the time when it was first diagnosed. In some conditions, live expectancy is severely reduced like Duchenne’s while in others it remains fair and sometimes has a good outlook.