Comparison between fibromyalgia, polymyalgia rheumatica, myositis and rheumatoid arthritis

Clinical presentation for fibromyalgia

Typical patient is a female between 30 and 50 years of age
Symptoms include:
- Pain
  - Should be present for at least 3 months
  - Pain is felt in muscles and joints, but there is no underlying physical manifestation of the pain
  - Pain is likely due to aberrant neuropathic mechanism
  - Pain tends to worsen with insomnia, cold and humid weather
- Headache
- Fatigue
- Non-restorative sleep
- Cognitive dysfunction (fibro-fog)
  - Poor memory
  - Difficulty concentrating
  - Lack of clear thought
Commonly associated with:
- Mood disorders
  - Anxiety and depression
- Functional somatic syndromes (chronic conditions with no identifiable organic cause
  - IBS
  - Tension or migraine headaches
  - Chronic fatigue syndrome
- Severe menstrual pain
- Lower UTI symptoms
- Tempomandbular pain

How to diagnose fibromyalgia?

Criteria for diagnosis
- Diffuse body pain present for at least 3 months
- WPI >= 7/19 and SS >= 5 OR WPI >= 3-6/19 and SS >= 9
- Symptoms may not be better explained by another illness
What is WPI and SS?
- Widespread pain index: self-reported number of areas in which pain is experienced over last 7 days (19 total areas)
  - Jaw (L, R)
  - Neck
  - Shoulder (L, R)
  - Upper arm (L, R)
  - Lower arm (L, R)
  - Chest
  - Abdomen
  - Upper back
  - Lower back
  - Hip/buttock (L, R)
  - Upper leg (L, R)
  - Lower leg (L, R)
- Symptom severity score: 4 questions
  - Indicate level of severity from 0 to 3 for fatigue
  - Indicate level of severity from 0 to 3 for non-restorative sleep
  - Indicate level of severity from 0 to 3 for cognitive symptoms including mood and memory
  - Indicate if the patient has anywhere from no symptoms to a great deal of symptoms from 0 to 3
According to the most recent Canadian guidelines, the 18 tender point examination (1990) is no longer required for diagnosis
- Traditionally, patients needed to have tenderness in 11/18 of the following areas of the body, with enough digital pressure that the thumbnail bed blanches
  - Lower anterior neck (2 points)
  - Second rib (2 points)
  - Occiput (2 points)
  - Trapezius, upper back (4 points, 2 on each side)
  - Lateral epicondyle (2 points)
  - Knees (2 points)
  - Greater trochanter (2 points)
  - Upper outer quadrant of guteal (2 points)
Laboratory investigations
- No laboratory test which can confirm fibromyalgia exists presently
- Laboratory testing is only conducted to rule out similarly presenting illnesses
  - CBC
  - ESR and CRP (inflammatory arthritis, polymyalgia rheumatica)
  - TSH (hypothyroidism)
  - CK (myopathies)

Differential diagnosis for fibromyalgia

Inflammatory rheumatological diseases
- Rheumatoid arthritis
- Inflammatory spondyloarthritis
- Systemic lupus erythematosus
- Polymyalgia rheumatica
- Myositis
Neurological conditions
- Multiple sclerosis
- Neuropathies
  - Presents with more localized pain compared to FM
- Myopathies
Hypothyroidism
- Ill-defined pain and fatigue
Depression
- Presents with more generalized pain compared to FM
Medication side effects
- Statins
- Aromatose inhibitors for breast cancer
- Bisphosphonates
- Bony metastases

Fibromyalgia vs polymyalgia rheumatica vs myositis vs. rheumatoid arthritis

Polymyalgia rheumatica

Inflammatory rheumatic disease
Associated with giant cell arteritis
Clinical presentation
- Pain is not from muscle but from tissues surrounding muscle
- This is why CK is usually normal
- Pain and stiffness of shoulders, neck and hips
- Improve after activity
- Constitutional symptoms: fever, weight loss, loss of appetite, night sweats
Diagnosis
- Increased ESR and CRP
- Normal CK
- Normochromic anemia
Treatment
- Low dose oral glucocorticoids
- Eventually taper and stop glucocorticoids if symptoms improve

Dermatomyositis and Polymyositis

Clinical presentation
- Polymyositis is inflammatory myopathy causing proximal muscle weakness (pelvis and shoulder)
- Dermatomyositis is polymyositis but also skin involvement
  - Gottron papules – erythematous papules on the dorsal surface of hand
  - Heliotrope rash – erythematous rash on upper eyelids
Diagnosis
- Elevated muscle enzymes
  - Increased CK
  - Increased AST, ALT
  - Increased LDH
- Increased ESR and CRP
- Myositis specific antibodies (useful for determining prognosis and response to treatment)
  - Anti-Jo-1
  - Anti-Mi-2
  - Anti-SRP
- Other tests
  - Abnormal EMG
  - Muscle biopsy
Treatment
- Corticosteroids
- Immunosuppresants

Rheumatoid arthritis

Inflammatory rheumatologic disease defined by joint pain
Clinical presentation
- IN CONTRAST TO polymyalgia rheumatica, distal joints are more affected in RA
  - MCP
  - PIP
  - DIPs are usually spared
  - Knees
  - Wrist joints
  - Cervical spine may be affected
- Morning stiffness of > 30 mins
- Extra-articular manifestations include
  - Constitutional symptoms
  - Rheumatoid nodules (non-tender subcutaneous bump)
  - Pleuritis
  - Pericarditis
  - Anemia of chronic disease
Diagnosis
- Using ACR criteria
- Laboratory tests
  - Increased ESR and CRP
  - Increased ferritin
  - Anemia of chronic disease
  - Anti-CCP is very specific and moderately sensitive
  - ANA
  - Rheumatoid factor
Treatment
- Methotrexate
  - First line
  - Highly effective
  - Many side effects
    - GI side effects
    - Abnormal liver enzymes due to hepatotoxicity
    - Bone marrow suppression
    - Pneumonitis and pulmonary fibrosis
    - Nephrotoxicity
  - Methotrexate is a folic acid antimetabolite – provide folate within 48 hours of starting methotrexate
- TNFa inhibitors if severe disease remains after 3 months of methotrexate

RF is sensitive for rheumatoid arthritis (but sensitive is lower in the first few months of disease onset). Anti-CCP is specific for rheumatoid arthritis.

ANA is sensitive for SLE while anti-double stranded DNA antibodies are specific for SLE.

How to manage fibromylagia?

Pharmacologic treatment
- Progression of pharmacologic treatment
  - Simple analgesics
  - TCA
    - Amitriptyline is a good TCA to start with
    - Has anticholinergic (mouth dryness, blurry vision, urinary retention, constipation) and anti-histamine (drowsiness) effects
  - SSRI, SNRI also show positive effects for pain, fatigue, depression and quality of life (pain reduction is still better for TCAs though)
    - E.g. duolextine, paroxetine, fluoxetine, sertraline
  - Pregabalin and gabapentin (anti-convulsants)
  - Opioids – last resort
    - Tramadol (weak opioid) is the only opioid that has been thoroughly studied for use in FM
    - Reserved for patients who are non-responsive to other forms of therapy
    - Avoid use of strong opioids
Non-pharmacologic treatment
- Improved mental well-being is associated with reduced pain intensity in FM
  - CBT
  - Group therapy
- Exercise
  - Aerobic exericse
  - Yoga