Muscle Injuries and Disorders

Muscle is a tissue of the body specialized for movement. There are 3 types of muscle in the body:

• Cardiac muscle is only found in the heart.
• Smooth muscle is found in the internal organs.
• Skeletal muscle hangs from our skeletons and allows us to move.

In general, skeletal muscle is under voluntary control whereas the other 2 types of muscles are controlled automatically from our brains.

People with problems of skeletal muscle usually present with complaints of pain, stiffness or weakness. 

Muscle pain and pain caused by other structures in the body can be difficult to identify because muscle overlies many different types of structures including the bursa , joints, and bone.

Additionally, muscle weakness may not necessarily indicate a problem with the muscle since an issue with the nerve can also demonstrate similar symptoms. Your doctor will use a combination of history, physical exam, lab tests, and imaging to help distinguish between the different possibilities.

Muscle pain/weakness in autoimmune disease

People with autoimmune conditions such as scleroderma, vasculitis and myositis, can experience muscle pain many times because of the symptoms linked with the condition. These can include:

• flare of underlying autoimmune condition
• toxicity of a medication or drug
• infection
• hormonal and genetic illnesses
• fibromyalgia

Muscle pain/weakness and myositis

Inflammation of muscle, or myositis, can be seen in patients with scleroderma, vasculitis, and inflammatory myopathy. Common symptoms include:

• muscle weakness
• evidence of inflammation on muscle biopsy
• elevated muscle enzymes in the blood

Inflammatory myopathy includes the illnesses polymyositis, dermatomyositis, inclusion body myositis, overlap myositis, and necrotizing autoimmune myopathy. In these conditions, the muscles are the major target of inflammation.

In scleroderma, 13% of people may have myositis and up to 90% will have some type of muscle involvement such as pain or stiffness.

Muscle involvement is not common in the ANCA associated vasculitides such as Churg-Strauss or Wegener’s granulomatosis, but there are case reports of this happening. 

In polyarteritis nodosa, muscle involvement is seen in 51% of the cases with muscle pain being the most common symptom of the disease. 

Mixed connective tissue disease is a condition associated with a particular autoantibody called anti-ribonucleo protein (anti-RNP). This condition is characterized by an overlap of scleroderma, myositis, and lupus. Between 50 and 70% of these patients will have also myositis.

Other causes of muscle weakness/pain

Several drugs can cause toxicity to muscle including statin drugs, hydroxychloroquine (Plaquenil), colchicine, and steroids.

Infections such as influenza, coxsackievirus, and Lyme disease can also cause muscle aches and weakness.

Hypothyroidism, hyperthyroidism, hyperparathyroidism and hypoparathyroidism can also cause problems with muscle.

Fibromyalgia is a condition where patients have diffuse muscle pain but there is no associated inflammation.

There are very effective ways to treat true muscle inflammation, but it is important to be sure that such inflammation is the cause of the problem. Your physician should be able to understand the reason for muscle complaints through a combination of careful questions, physical exam, blood tests, and sometimes more involved testing (such as EMG/Nerve conduction studies, MRI of muscle, or even muscle biopsy). 

Talking to your doctor early will allow them to prescribe a directed therapy plan to limit the problem’s effect on your life.