Dermatomyositis - 2001

Written by the Research Department at the Muscular Dystrophy Campaign.

Contents:

• Background information
• Current research
• Treatment options for dermatomyositis
• What does this mean for me now and in the future?

Background information

Dermatomyositis falls within a group of muscle disorders called inflammatory myopathies. The term 'dermatomyositis' comes from two words, 'dermato' meaning skin and 'myositis', which means inflammation of muscle. The condition is characterised by a distinctive rash commonly over the face, chest and knuckles and muscle weakness. Some individuals may also develop calcium deposits under the skin.

Inflammatory myopathies are thought, in the majority of cases, to be autoimmune disorders caused when the body's own immune system becomes faulty and begins to attack its muscle cells, but the exact cause has not been established. When this occurs the body sees its own muscle cells as foreign and produces highly specific molecules called antibodies to target muscle cells and destroy them. This is the same mechanism that operates in healthy individuals when they have an infection, the bacteria or virus is recognised as foreign and the body produces specific antibodies to target the bacteria or viruses and destroy it. It is a rare condition with an incidence of five per 10,000 people and shows a female predominance of 2:1. In some older patients dermatomyositis may be associated with an another condition, like cancer.

Current research

Research over the last couple of years has focussed mainly on therapeutic approaches to dermatomyositis.

The European Neuromuscular Centre based in the Netherlands is an organisation set up to stimulate and facilitate scientific collaboration in neuromuscular disorders throughout Europe. One of its functions is to promote workshops on specific neuromuscular topics and participants (clinicians/researchers working in the field) come together for three days to discuss developments and plan future directives. In January 1999 there was a workshop entitled "Therapeutic approaches to Polymyositis, Dermatomyositis and Inclusion Body Myositis". The results and discussions from this workshop have been published in the journal "Neuromuscular Disorders, Vol 11(1)". There was consensus amongst participants that there is a lack of controlled well-designed studies on therapeutic options for these disorders.

The aim of this workshop was to:

• stimulate international co-operation for further therapeutic investigations
• establish diagnostic criteria which could be used by clinicians for diagnosis and for future studies so that reliable data could be collected in trials

The ENMC meeting resulted in improved diagnostic criteria being established which will improve diagnosis and management of the condition in the future. These criteria are available on the ENMC website: www.enmc.org

Treatment options for dermatomyositis

There are three main categories:

1. Steroids
These are usually the initial choice of treatment and Prednisolone is commonly used. Steroids act by reducing the inflammation present in the muscles, however, especially at high doses, there can be severe side effects such as increase in weight gain, cataracts and osteoporosis. To reduce this the dosage is often reduced after a while or even given on alternate days, the aim is to find the lowest dosage that controls the symptoms.

2. Immunosuppressants
Types of immunosuppressants include:

(i) Azathioprine
(ii) Methotrexate
(iii) Cyclopyhosphamide
(iv) Cyclosporin

These act to suppress the immune response causing the inflammation. Use of these drugs is also associated with side effects and careful monitoring is required, it is a matter of obtaining a situation where the benefits outweigh the side effects associated with them.

3. Immunomodulation
(i) intravenous immune globulin (IVIG) - These are immunoglobulins which are molecules essential to the immune system that attach to foreign substances like bacteria and assist in destroying them, and are given intravenously. How they work is still a matter of debate but it is thought that they block the actions of those antibodies produced by the body and directed against the muscle. In 1993 a small, well designed trial for dermatomyositis using IVIG yielded results showing an improvement in muscle strength. Following this study IVIG became an established treatment option for dermatomyositis. Larger trials run for a longer period of time would be beneficial to a give clearer picture of the long term benefits associated with its use. The main disadvantage of this type of treatment are the high costs associated with it, the main side effect was headaches.

(ii) Plasmapheresis - this involves removing the abnormal antibodies

(iii) Total body irradiation - this is only used when all other treatments have failed and the objective is to reduce the numbers of immune cells in the body that can react.

The specialist will decide on the most appropriate method of treatment based on clinical history and will re-evaluate the situation depending on the progress of the disorder. It is therefore important that individuals receive monitoring and support from a specialist with expertise in this area.

Research is also ongoing into identifying the exact nature of the antibodies generated by the body in dermatomyositis. These antibodies are highly specific and have characteristics (markers) which enable scientists to detect them. Work such as this is important because it:

• improves the diagnosis
• may open up therapeutic options aimed at specifically destroying these cells

Transplantation of bone marrow cells, and recently the use of stem cells collected from blood has been used in the treatment of cancer and leukemia and this option has been investigated for its potential in treating autoimmune disorders. However, this would not be considered as a routine treatment and carries substantial risks and costs. It may be considered in the future for cases where the disease is severe and does not respond to any other form of treatment.

The reason for putting this into this section is twofold:

(i) There has been a lot of media attention lately regarding the potential of stem cells for therapeutic benefit in disorders, including muscle disorders. This application refers to muscle disorders that arise due to a faulty gene/s which causes the muscle cell to break down and should not be confused with dermatomyositis where the problem lies with the immune system. Treatment for muscle disorders such as Duchenne muscular dystrophy would involve the use of stem cells to replace the damaged muscle tissue with healthy new muscle cells. In the case of dermatomyositis the aim would be to remove the faulty immune cells and replace them with new stem cells that would not cause an immune reaction. This would involve the patient first undergoing a procedure (drug, chemo or radiation therapy) to eliminate all the immune cells causing the problem. These two applications of stem cells are not to be confused.

(ii) There was an international meeting in Basel, Switzerland in October 2000 the aim of which was to assess all existing data on the use of stem cell transplantation for treating severe autoimmune disorders. At this meeting data on 390 patients was analysed and of these five had dermatomyositis or polymyositis. The consensus was that clinical trials for autoimmune disorders (a very large category) should continue but to date there is no protocol for dermatomyositis.

What does this mean for me now and in the future?

In the majority of cases of dermatomyositis the treatment options discussed above are effective. There does however need to be further well-designed clinical trials to evaluate the current drug protocols and offer scientific based evidence to support their use. As mentioned above, the need for this has been established and is being addressed. If there were any results in the future that would have an impact on your condition, the Muscular Dystrophy Campaign will advise you of this.

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