Myositis
Myositis is the name for a group of conditions where there is muscle inflammatory changes and break down. It is usually autoimmune in nature. The main symptoms are weakness, painful or aching muscles which sometimes can be confused with joint or nerve related pain.
There are different types of myositis, including:
- Polymyositis, which affects many different muscles, particularly the shoulders, hips and thigh muscles. It’s more common in women and tends to affect people aged 30 to 60. This is the most common cause of myositis.
- Dermatomyositis, which affects several muscles and causes a rash. It’s more common in women and can also affect children (juvenile dermatomyositis).
- Inclusion body myositis (IBM), which causes weakness in the thigh muscles, forearm muscles and the muscles below the knee. It may also cause problems with swallowing (dysphagia). IBM is more common in men and tends to affect people over 50.
Polymyositis
Polymyositis affects many different muscles, particularly around the neck, shoulders, back, hips and thighs.
Symptoms of polymyositis include:
- muscle weakness
- aching or painful muscles and feeling very tired
- finding it hard to sit up, or stand after a fall
- swallowing problems, or finding it hard to hold your head up
- associations with poor mental health
Patients may find it difficult to get up from a chair, climb stairs, lift objects, and comb your hair. The muscle weakness can become so severe that even picking up a cup of tea can be difficult. The muscle weakness may change from week to week or month to month, although it tends to steadily get worse if treatment is not given early.
Case Presentation
Clinical history;
- 30 year old lady presents with left arm, shoulder and neck pain over the past 6 months
- Pain comes in flares every few weeks and described as a dull ache
- Left arm feels heavy and pain on lifting and carrying, initially carrying weight in gym, progressing to household objects e.g., kettle
- Mild tingling in the left hand on occasions
- Night pain present during flares
- No temperatures, fevers or night sweats
- No blood in urine (to indicate haemoglobinuria)
Previous treatment and investigation
- GP organised MRI scan of neck which showed no evidence of cervical nerve root impingement.
- Patient had physiotherapy to treat neck symptoms which helped marginally
Past Medical history;
- BMI 22
- Non-smoker
- History of inflammatory bowel disease (IBD), previously been on immunosupressants mercaptopurine and asacol (stopped 6 years ago and no recent flares)
- Hypothyroidism – taking thyroxine 50mcg for underactive thyroid
Exercise history;
- Enjoys keeping fit with exercise classes and gym training
- No execessive heavy loading history or history of endurance sports
Social history;
- Teacher
- Non drinker or smoker
Clinical examination;
- Moderate discomfort on shoulder movements particulary, adduction and abduction and wrist movements
- Full power in all myotomes in left upper limb and normal sensation in all dermatomes
- Moderate/severe pain on palpation of certain muscle groups including deltoid, forearm
- Neural tension tests mildly positive in median and radial nerve bias
Point of Care Ultrasound
Normal appearences of the shoulder, rotator cuff, deltoid, elbow and wrist
Clincial suspicions, differentials and reasoning;
- Myositis. The past medical history of inflammatory bowel disease should raise suspicion for inflammatory causes of muscle pain and should be excluded before a musculoskeletal diagnosis in made. Localised tenderness over muscle groups is high suggestive of muscle pathology (inflammation or otherwise).
- Rhabdomyolosis. Rhabdomyolysis can be defined as a clinical syndrome associated with the breakdown of skeletal muscle fibres and myocyte cell membranes, leading to release of muscle contents into the circulation, resulting in multiple complications, including electrolyte disturbance. This can occur in patients with extreme loading e.g. ultramarathon, or exercising in a dehydrated state. Unlikely in this patient due to the low training volume. Note, severe myositis can lead to rhabdomyolosis.
- Shoulder related pain. Both glenohumeral and subacromial pain can present as referred symptoms down the arm but usually have restriction/pain in shoulder range rather than global muscle aching and fatigue, although this can be difficult to differentiate. Tenderness to the muscles in arm would also suggest there is localised pathology.
- Nerve related pain. Although previous MRI of the cervical spine came back as normal, neural tension and nerve related pain can arise in the neck, brachial plexus or in upper/lower arm. Normal neurological examination of myotomes/dermatomes would suggest otherwise in this case. Pain is also out of proportion to fit with neural tension with no median or radial nerve disturbance.
Imaging and Investigation
MRI scan left shoulder, left upper arm and foream
T2 weighted images show florid muscle oedema and myositis in teres major (left image), posterior delotid (middle image), brachoradialis and forearm compartments (right image)
Blood tests
- Elevated ESR of 56
- Elevated creatine kinase (CK) of 560 (CK is a marked of muscle breakdown)
- Positive Myositis autoantibodies
- Normal kidney, liver and blood count
Diagnosis
Polymyositis, affecting muscle groups in the left upper liimb. Likely association with patient’s previous inflammatory bowel disease and hypothyroidism.
Management
Exercise therapy
- Patient given an appropriate loading programme with aerobic, anaerobic and strength stimuli
- When treating inflammatory myositis, exercise is safe and very beneficial in the reduction of inflammation
- This is different to overuse muscle breakdown conditions (e.g. rhabdomyolsis) where peroids of rest may be advised to aid muscle recovery
Medical treatment
- Patient urgently referred to NHS rheumatology service and started on immunosuppressants
- Patients symptoms settled rapidly once started on the correct treatment
Key Summary and learning points
- Be mindful of pain localised to muscles, particularly in the proximal upper and lower limb girdles
- A good inflammatory history is key if suspecting myositis, although there is not always a clear association between inflammatory bowel disease and inflammatory joint or muscle disease
- Blood tests and autoantibodies have an important role when diagnosing myositis, particularly ESR and and Creatine Kinase.
- Aerobic or static exercise is safe and will not cause damage to the muscles or joints in people with myositis
- Regular physical activity can also reduce the risk of chronic diseases that are possible complications of myositis, including type II diabetes, osteoporosis, cardiovascular disease and hypertension
- Exercise is particularly important for patients with inclusion body myositis (IBM), as this type of myositis does not respond to medication
- Ultrasound often cannot detect muscle oedema, whereas MRI is much more sensitive
- Useful link for patients and clinicians https://www.myositis.org.uk/
