Neurological Disorders: Inflammatory Myopathies

Introduction

Inflammatory Myopathies, as the name implies are myopathies (muscle diseases) due to inflammation.

Inflammation is a natural process that helps in defending as well as healing of the body. However sometimes this process takes place without any need for it and then it causes pathological conditions like above.

These muscle diseases are also considered as autoimmune diseases, meaning the immune system instead of protecting paradoxically attacks the tissues or organs in the body; muscles in this context.

The three types of inflammatory-myopathies are;

• Polymyositis
• Dermatomyositis
• Inclusion body myositis (IBM) – sporadic or hereditary types

Clinical manifestations

Progressive muscle weakness is the main manifestation for all these diseases. Large proximal muscles like the shoulder and hip area are affected first with the first two conditions where as with the IBM the distal muscles are also usually affected from the beginning.

Because of proximal weakness patients will have difficult in getting up from a sitting or a lying position, and difficulty raising the arms above the shoulder level. The distal weakness in IBM usually presents as foot drop and/or wrist drop, difficulty in using the hand for various daily activities etc.

Due to muscle inflammation there may be sore feeling in the muscles.

As disease progresses muscle atrophy (thinning) takes place.

A skin rash is characteristically seen with dermatomyostis.

Diagnosis

• Blood CPK,LDH, aldolase etc
• EMG/NCS (electromyography/nerve conduction studies)
• Muscle biopsy

With muscle biopsy inflammatory cells are seen in all these 3 diseases however an inclusion body is seen only with IBM.

Treatment

The following agents are usually employed;

• Steroids
• Other immunosuppressive agents like azathioprine, cyclosporine etc
• Intravenous Immunoglobulins
• Plasmapheresis etc

IBM is very resistant to any of these therapies.

A neurologist is commonly involved in the care of patients with inflammatory myopathies.

Additional note…

The presence of dermatomyositis and polymyositis especially the first one warrants an evaluation for underlying tumors in the body because incidence of tumor is high. Incidence of certain autoimmune connective tissue disorders is also high with these conditions.



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