LECTURE 8 (Muscle disorders) Flashcards
What is Polymyalgia Rheumatica?
An inflammatory disorder with an unknown cause that usually occurs in older patients (>50 years)
SYMPTOMS:
- bilateral proximal muscle stiffness [neck/torso, shoulders/proximal arms, hips/proximal thighs] -> worse in morning + often difficult dressing
- DOES NOT CAUSE MUSCLE WEAKNESS [strength testing normal + normal CK level since no muscle damage just inflammation]
- muscle pain (especially in shoulder)
- malaise, fever, fatigue
LAB FINDINGS
- elevated CRP + ESR (due to inflammation)
- responds well to glucocorticoids
DIAGNOSIS:
no test required -> diagnose if patient has symptoms + signs of inflammation
Commonly occurs with temporal arteritis
What is Fibromyalgia?
A chronic pain disorder where patients develop a widespread musculoskeletal pain and is common in women between 20-55 years old
EPIDEMIOLOGY:
30-50% have corresponding depression/anxiety
DIAGNOSIS:
- unknown cause
- diagnosed clinically (with symptoms)
- normal muscle biopsy
- normally tests
SYMPTOMS:
- point tenderness on exam (usually in specific anatomic locations)
TREATMENT:
- exercise
- tricyclic antidepressants (amitriptyline)
- SSRIs
What are Inflammatory myopathies?
Autoimmune muscle disorders that involve muscle inflammation
TWO MAJOR DISORDERS:
- Polymyositis
- Dermatomyositis
- usually involve skeletal muscle (weakness)
- can involve the heart (can lead to myocarditis + decreased myocardial function)
What is the diagnosis and treatment for Inflammatory myopathies?
DIAGNOSIS:
- muscle biopsy
TREATMENT:
- immunosuppression
[usually corticosteroids (prednisone) initially then steroid sparing drugs long-term (azathioprine/methotrexate)
What are the clinical manifestations of Inflammatory myopathies?
- Myalgias (muscle pain)
- Slow onset symmetric muscle weakness
- Proximal muscle weakness at first (HALLMARK!!!) -> difficulty rising from chair, difficulty climbing stairs, difficulty combing hair
- Distal weakness occurs later in disease
How can you distinguish Polymyalgia Rheumatica and Inflammatory myopathies if they both involve proximal muscles?
Polymyalgia Rheumatica does not involve muscle weakness (only muscle pain + stiffness) whereas Inflammatory myopathies involve muscle weakness
What are the Lab findings in Inflammatory Myopathies?
- Elevated creatinine kinase (CK)
[ongoing inflammation of muscle tissue + muscle cells spilling CK into the serum] - Elevated ESR (due to inflammation)
- Anti-nuclear antibodies (ANA) +ve [but not specific for myopathies, found in lupus too]
- Anti-Jo1 antibodies
[antibody directed against Histidyl t-RNA synthetase + most common myositis antibody]
What is the difference between Polymyositis and Dermatomyositis?
POLYMYOSITIS
- Endomysial inflammation
[Endomysium = connective tissue surround each muscle fibre]
- Predominant cell type is CD8+ T-cells
DERMATOMYOSITIS
- Skin changes
- Perimysial inflammation
- CD4+ T-cells
[Perimysium = connective tissue surrounding fascicles (bundles of fibers)]
What are the classic skin findings in Dermatomyositis?
- Heliotrope rash
[purple discolouration of upper eyelid] - Gottron papules
[symmetric, scaly papule appearing on hand + finger joints]
Both are pathognomonic for dermatomyositis -> muscle weakness + these symptoms -> definitive diagnosis
What are the other skin findings of Dermatomyositis?
- Malar rash (similar to Lupus)
- “Shawl and V signs”
[red-brown discolouration of skin that occur in sun exposed areas -> upper back = looks like a shawl, neck/upper chest = V sign] - Mechanic’s hands
[cracks/fissures on palms with increased pigmentation]
Describe malignancy associated with inflammatory myopathy
- Mechanism is unclear
- Stronger evidence for Dermatomyositis malignancy than Polymyositis malignancy
- Associated with increased risk of adenocarcinomas
[cervix, lung, ovaries, pancreas, bladder, stomach]
