Flashcards in Muscle diseases Deck (28):
How do muscle diseases present?
Muscle weakness/ tiredness
Abnormal blood tests
disease of the muscle
Idiopathic inflammatory myopathy that causes symmetrical, proximal muscle weakness
Histology of polymyositis (and dermatomyositis)
Muscle fibre necrosis, degeneration, regeneration and an inflammatory cell infiltrate.
Presentation of polymyositis
Proximal (usually symmetrical) muscle weakness in the limbs (e.g. upper arms, upper legs).
It is insidious in onset (presents over several months).
Often patient presents with specific problems such as difficulty brushing hair etc.
Pathogenesis of polymyositis and dermatomyositis
T-cell–mediated cytotoxic process directed against unidentified muscle antigens. CD8 T cells, along with macrophages, initially surround healthy nonnecrotic muscle fibers and eventually invade and destroy them.
An autoimmune response to nuclear and cytoplasmic autoantigens is detected in about 60-80% of patients with polymyositis and dermatomyositis. Some serum autoantibodies are shared with other autoimmune diseases (ANA, anti-RNP antibody), and some are unique to myositis (anti-Jo-1, anti-SRP antibodies).
Systemic diseases that accompany polymyositis and dermatomyositis
Can be accompanied by dysphagia- secondary too oropharyngeal and esophageal involvement. This is a poor prognostic sign
Interstitial lung diseases.
Investigations into polymyositis and dermatomyositis
Inflammatory markers are often raised.
Serum creatine kinase (CK) level is usually raised, often more than 10 times the normal level.
Autoantibodies include ANA, anti-Jo-1 and anti-SRP.
MRI- used to assess extent of muscle involvement
Electromyographic (EMG) findings are abnormal in almost all patients
MUSCLE BIOPSY is crucial in helping to diagnose polymyositis and in excluding other rare muscle diseases. Muscle biopsy shows muscle fibres in varying stages of inflammation, necrosis, and regeneration
Treatment of polymyositis and dermatomyositis
Prednisolone (initially around 40mg) combined with disease modifying drugs such as methotrexate or azathioprine
Idiopathic inflammatory condition.
Clinical features of dermatomyositis
Proximal muscle weakness
Worsens over months
Gottrons papules- scaly red patches over the knuckles, knees and elbows.
Heliotrope rash- purply pink discolouration around the eyes
Shawl sign- red rash that comes down in a v shape at the front of the chest
Which disease, polymyositis or dermatomyositis, has a higher malignant potential? And where do they commonly metastasise too?
Ovarian, breast, stomach, lung, bladder and colon cancer.
Presentation of dermatomyositis
Tired muscles, functional difficulty, muscle pain
Drugs- statins and steroids.
Other medical conditions- e.g. DM or thyroid disease.
Social- alcohol and ellicit drug use
Other symptoms- weight loss, cough, breathlessness, Raynauds.
On examination of polymyositis and dermatomyositis, which tests would you perform?
Confrontational testing- directly pushing against the muscle to see if it is strong.
Isotonic testing- 30 second sit to stand test.
Inclusion body myositis
Often misdiagnosed as polymyositis. Patient is often older (>50 years), and presents as distal muscle weakness.
Wrist and flexor muscles in upper limb, anterior tibial muscles and quadriceps in lower limbs.
On biopsy- what does inclusion body myositis show?
Relatively common chronic inflammatory condition. Almost always in elderly (>50). Associated with temporal arteritis/giant cell arteritis.
How does polymyalgia rheumatica present?
Proximal myalgia in the hip and shoulder girdles- symptoms occur over a few weeks. Presents as aching shoulders and morning stiffness.
After moving around for a bit they tend to get better, then sore again before going to bed or at periods of rest.
Muscle strength is normal
Giant cell arteritis/ temporal arteritis
Vasculitis of the temporal artery. Granulomatous deposit in the artery.
Features of giant cell arteritis
Tender, enlarged, non-pulsatile temporal arteries.
Treatment of polymyalgia rheumatica
Rapid and dramatic response to low dose steroids.
If the patient has temporal arteritis- higher dose steroid required.
Gradual reduction in steroid dose for around 18 months to 2 years.
Diagnosis of polymyalgia rheumatica
Raised CRP and PV/ESR are almost always the case in polymyalgia rheumatica.
Temporal artery biopsy should be used for GCA
Common cause of MSK pain- not associated with inflammation. It is an unexplained condition that affects anyone (however is commonest in young and middle aged women).
Pathogenesis of fibromyalgia
Disorder of central pain processing or a syndrome of central sensitivity. Patients tend to have a lower threshold of pain and of other stimuli, such as heat, noise, and strong odours
Presentation of fibromyalgia
Persistent (>3 months) widespread pain. Pain can be around the neck and lower back- but patients often describe it as 'hurting everywhere'.
Fatigue- disrupted sleep
Cognitive difficulties- find it difficult to concentrate.
Multiple unexplained conditions such as anxiety and depression.
Symptoms often become worse with exertion and stress.
Clinical findings of fibromyalgia
Excessive tenderness on palpation of soft tissues
11/18 tender points
No other abnormality of musculoskeletal system
Diagnosis of fibromyalgia
No diagnostic tests
Inflammatory markers normal
Absence of other explanation of symptoms