Bay Biosciences provides high quality, clinical grade, cryogenically preserved sera (serum) and matched K3-EDTA plasma samples from myasthenia gravis (MG) patients.

The sera (serum) and K3-EDTA plasma specimens are processed from myasthenia graves (MG) patient’s peripheral whole-blood using customized collection and processing protocols.


Myasthenia Gravis (MG) Overview

Myasthenia gravis (MG) is a neuromuscular disorder that causes weakness in the skeletal muscles, which are the muscles your body uses for movement.

MG happens when communication between nerve cells and muscles becomes impaired. This impairment prevents crucial muscle contractions from occurring, causing muscle weakness.

“Myasthenia gravis” means “grave muscle weakness,” but many cases are mild, and life expectancy is normal.

In MG the muscles around the eyes tend to be affected first, causing the eyelids to droop. Patients may experience double vision, weakness in the arms and legs, and difficulties chewing, swallowing, speaking, and breathing. Involuntary muscles, such as the heart muscles, are not affected.

Symptoms often worsen with physical activity and improve after resting or a good night’s sleep. There is no cure, but treatment can relieve and even remove symptoms.

According to the Myasthenia Gravis Foundation of America, MG is the most common primary disorder of neuromuscular transmission.

MG is considered a relatively rare condition that affects about 20 out of every 100,000 people in the United States. However, it’s also underdiagnosed, so the prevalence could be higher.

The condition affects 14 to 20 people in every 100,000 in the United States, or between 36,000 and 60,000 people. It can happen at any age, but it is more likely to affect women before the age of 40 years, and men after the age of 60 years.


Who is at Risk of Developing Myasthenia Gravis (MG)

Myasthenia gravis affects all races and can develop at any age from childhood to extreme old age. Young patients are more commonly women, whereas older patients, over the age of 50, are more often men.

Patients who inherit a tendency to develop an autoimmune condition are at increased risk of developing myasthenia gravis, so a patient with myasthenia gravis may have, or have a relative with another autoimmune condition such as diabetes or thyroid disease.

Occasionally, myasthenia gravis develops in patients with rheumatoid arthritis (RA) who are given the drug penicillamine. In these cases, the myasthenia gravis symptoms usually disappear when the drug is stopped.


Is Myasthenia Gravis (MG) Inherited

Myasthenia gravis is not an inherited condition and does not usually occur in families. This is in contrast to the congenital myasthenic syndromes that are genetic conditions.

However, it is thought that a person’s genetic make-up is one of perhaps many factors that lead them to develop myasthenia gravis, and it may occasionally be found in more than one family member.


Signs and Symptoms of Myasthenia Gravis (MG)

Primary symptom of MG is weakness in the voluntary skeletal muscles, which are muscles under your control.

The failure of muscles to contract usually happens because they can’t respond to nerve impulses. Without proper transmission of the impulse, the communication between nerve and muscle is blocked and weakness results.

Symptoms of MG may present via the following body parts:

Arms and Legs

MG can also affect the muscles in your arms and legs, leading to the following symptoms:

  • Fatigue
  • Overall weakness in your legs
  • Problems walking up stairs or lifting objects 
  • Weakness in your fingers, hands, and arms

Chest

When MG affects the muscles of the chest area, you may experience severe and potentially life threatening symptoms:

  • Respiratory failure, caused by weakness in the diaphragm and chest muscles that may lead to myasthenic crisis and is considered an emergency

Eyes

MG can cause dropping of the eyelids, as well as double or blurry vision. You may also experience overall weakness in your eye muscles.

Drooping in one or both eyelids, double vision, or both are an early sign in 2 out of every 3 patients. This can cause eyesight problems, and it is known as ocular myasthenia gravis.

Face

In addition to facial paralysis, MG may lead to changes in the patients facial expressions. One in six MG patients, the throat and face muscles are the first to be affected.

Not everyone will have every symptom, and the degree of muscle weakness can change from day to day. The severity of the symptoms typically increases over time if left untreated.

Additional MG Problems

MG patients may have following additional issues:

  • When the individual drinks, liquid may come out of the nose.
  • Chewing: The muscles used for chewing may weaken during a meal, especially if the food is hard or chewy, such as a steak.
  • Facial expressions: A different or unusual smile may develop if certain facial muscles are affected. 
  • Speaking: Speech may become soft or nasal.
  • Swallowing: The patient may choke easily, and eating, drinking, and swallowing pills becomes harder.

Limb weakness is the first sign in 10 percent of patients. The arm and leg muscles may weaken, affecting activities such as lifting or walking.

When limb muscles are involved, other muscles also tend to be affected, such as the throat, eyes, or face.

Symptoms fluctuate and are typically worse at the end of the day, in hot weather, during or immediately after an infection, or during menstruation.


Causes of Myasthenia Gravis (MG)

Antibodies

Myasthenia gravis develops in adult life as the result of a defect in the immune system. The immune systems job is to produce antibodies against bacteria and viruses. Unfortunately, it sometimes produces antibodies against ‘self’ proteins causing ‘auto’ immune disease.

The majority of patients with myasthenia gravis produce antibodies against a self-protein called the acetylcholine receptor (AChR).

About 85 percent of patients with myasthenia gravis produce antibodies against a protein called the ‘acetylcholine receptor’ (AChR). This is found at the neuromuscular junction and acts as a receiver for the chemical signal ‘acetylcholine’ (ACh) that is released from the nerve to tell a muscle to contract.

The antibodies bind to the acetylcholine receptors on the surface of the muscle and greatly reduce their ability to receive the chemical signal. As a result, the person experiences muscle weakness, which becomes worse as they repeatedly try to use the same muscle.

Many patients with myasthenia gravis who don’t have antibodies to the AChR, have antibodies to a protein called ‘muscle-specific kinase’ (MuSK).

This protein helps organise ACh receptors on the muscle cell surface. Research is ongoing to find out what antibody is responsible in the approximately 10 percent of individuals who don’t have antibodies to AChR or MuSK. Recently, antibodies to a protein called ‘LRP4’ were found to be the cause for some of these patients.

Scientists don’t know what triggers most autoimmune conditions, but they have a few theories. One possibility is that certain viral or bacterial proteins mimic ‘self-proteins’ in the body (such as AChR), stimulating the immune system to accidentally attack it.

In the case of MG, the antibodies block or destroy muscle receptor cells, resulting in fewer available muscle fibers. As a result, the muscles cannot contract properly, and they easily become tired and weak.

Although we now understand how antibodies to the acetylcholine receptor cause muscle weakness, we do not know why patients with myasthenia gravis develop these particular antibodies.

Thymus Glad Irregularities

In some cases, the thymus gland in the chest appears to be important in triggering the abnormal immune response.

The thymus gland is large during infancy and continues to grow until puberty. After this, it gets smaller and eventually is replaced with fat. A significant number of adult patients with MG have an abnormally large thymus gland, and about 1 in 10 patients with MG have a benign tumor in the thymus gland.

Some medications or viruses may trigger the onset of MG. Drugs that may cause a worsening of symptoms in susceptible patients include beta blockers, calcium channel blockers, quinine, and some an antibiotics.

It’s also possible to develop benign or cancerous tumors of the thymus gland, which may interfere with important immune cell production, like T-cells. The enlarged thymus gland also produces antibodies that block acetylcholine.

According to the MDA, about 75 percent of people with MG have thymus gland irregularities (thymic hyperplasia )and another 15 percent have tumors.

As a result, the thymus gland may give your immune system incorrect instructions, which researchers believe may lead to immune cell destruction that causes MG.

Age Plays a Role

While MG may develop at any age, it’s most common in people over the age of 40. Women are more likely to be diagnosed as younger adults, whereas men are more likely to be diagnosed at 60 or older.

About 10 to 15 percent of MG cases develop in childhood, but most children achieve remission.

It’s also possible for newborn babies to have a temporary condition called neonatal myasthenia. This occurs when the mother has MG and passes on the antibodies to a fetus. However, neonatal myasthenia is temporary, lasting about 2 to 3 months post-delivery.

Genetics

Genetic factors may play a role in developing myasthenia graves (MD).

Symptoms may also worsen with emotional or mental stress, illness, tiredness, or a high fever.

Neonatal myasthenia affects newborns if they acquire antibodies from a mother who has MG. The symptoms usually disappear in 2 to 3 months, and MG in infants and children is rare.

Other Causes

Rarely, mothers with myasthenia gravis have children who are born with myasthenia gravis (neonatal myasthenia gravis). If treated promptly, children generally recover within two months after birth.

Some children are born with a rare, hereditary form of myasthenia gravis, called congenital myasthenic syndrome.

Complications of Myasthenia Gravis

Complications of myasthenia gravis are treatable, but some can be life-threatening. Following are some of the complications of myasthenia graves (MG).

Myasthenia Gravis Crisis

A crisis occurs when the muscles involved in respiration are affected. Symptoms include shortness of breath and breathing problems. This is a medical emergency that needs hospitalisation and prompt medical treatment, including the use of a ventilator to assist breathing.

Some of the triggers of myasthenic crisis include physical stress, pregnancy or infection. When myasthenia is properly treated, crisis is very rare. And when crisis does occur, it has a good rate of recovery, thanks to a wide range of treatments and the quality of respiratory care at most hospitals.

Thymus Gland Tumors

Some patients with myasthenia gravis have a tumor in the thymus gland, a gland under the breastbone that is involved with the immune system. Most of these tumors, called thymomas, are not malignant or cancerous.

Other Disorders

Patients with myasthenia gravis are more likely to have the following conditions:

  • Underactive or Overactive Thyroid: The thyroid gland, which is in the neck, secretes hormones that regulate your metabolism. If your thyroid is underactive, you might have difficulties dealing with cold, weight gain and other issues. An overactive thyroid can cause difficulties dealing with heat, weight loss and other issues. 
  • Autoimmune Conditions. Patients with myasthenia gravis might be more likely to have autoimmune conditions, such as rheumatoid arthritis (RA) or lupus.


Diagnosis of Myasthenia Gravis (MG)

A doctor may suspect myasthenia gravis, if a patient has drooping eyelids but no problem feeling things, and if they are prone to muscle weakness that improves after rest.

Diagnosis can be difficult, however, because MG shares symptoms with other conditions. A neurologist may need to confirm the diagnosis.

Patients whose muscles are weak because of MG respond well when ice is applied to the affected area. Some doctors try this initially as they gather data to help them make a diagnosis.

If an individual’s physical examination and medical history reveals a pattern of weakness that suggests myasthenia gravis, further tests done to confirm the diagnosis include:

  • A blood test can detect the presence of antibodies to the acetylcholine receptor (AChR) or MuSK.The majority of patients with myasthenia gravis have antibodies to one of these proteins and this confirms the diagnosis of myasthenia gravis.
  • Electromyography (EMG) uses electrodes to stimulate muscles and evaluate muscle function. Muscle contractions that become progressively weaker may indicate myasthenia gravis.
  • The ‘Tensilon test’ is often used to diagnose myasthenia gravis. It involves an injection of a drug called Tensilon, which temporarily improves muscle strength in people with myasthenia gravis.
  • Chest x-ray, CT scan or MRI may be performed to examine the thymus gland, because abnormalities of the thymus are often linked with myasthenia gravis.

A pulmonary function test, or spirometry, assesses how well the patient can breathe by measuring the maximum amount of air a person can expel from the lungs after breathing in deeply.

Performed regularly, this test can help to monitor any gradual worsening of muscular weakness in the lungs. This is especially important for patients with severe symptoms, to avoid severe breathing problems.

Muscle biopsy can be done to eliminate another muscular condition.


Treatment of Myasthenia Gravis (MG)

There is currently no cure for myasthenia graves (MG). The goal of treatment is to manage symptoms and control the activity of the immune system.

Medication

Corticosteroids and immunosuppressants can be used to suppress the immune system. These medications help minimize the irregular immune response that occurs in MG.

Additionally, cholinesterase inhibitors, such as pyridostigmine (Mestinon), can be used to increase communication between nerves and muscles.

Thymus Gland Removal

Removal of the thymus gland (thymectomy), which is part of the immune system, may be appropriate for many patients with MG. Tumors, even those that are benign, are always removed because they may become cancerous.

Once the thymus is removed, patients typically show less muscle weakness. Research also shows that thymectomy results may be more effective in those who also take prednisone.

Plasma Exchange

Plasmapheresis is also known as a plasma exchange. This process removes harmful antibodies from the blood, which may result in an improvement in muscle strength.

This is a short-term treatment. The body continues to produce harmful antibodies, and weakness may recur. Plasma exchange is helpful before surgery or during times of extreme MG weakness.

Intravenous Immune Globulin

Intravenous immune globulin (IVIG) is a blood product that comes from donors. It’s used to treat autoimmune MG. Although it’s not entirely known how IVIG works, it affects the creation and function of antibodies.

Lifestyle Changes

There are some things you can do at home to help alleviate symptoms of MG:

  • Get plenty of rest to help minimize muscle weakness.
  • If you’re bothered by double vision, consult with your doctor about whether you should wear an eye patch.
  • Avoid stress and heat exposure, since both can worsen symptoms.

These treatments cannot cure myasthenia gravis. However, you’ll typically see improvements in your symptoms. It’s also possible to go into remission, during which treatment is not necessary.


Prevention of Myasthenia Gravis (MG)

MG cannot be prevented. However, a person can take steps to stop a flare-up of symptoms or prevent them from developing complications.

These include practicing careful hygiene to avoid infections, and treating them promptly if they do occur.

It is also advisable to avoid extreme temperatures and overexertion. Effective stress management can also reduce the frequency and severity of symptoms.

 

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