Muscle diseases Flashcards
What is dermatomyositis
inflammatory disorder causing symmetrical, proximal muscle weakness and characteristic skin lesions
Cause of dermatomyositis
Idiopathic
Associated with other connective tissue disorders or malignancy
What malignant conditions are associated with dermatomyositis
ovarian cancer
breast cancer
lung cancer
What is polymyositis
A variant of dermatomyositis but without dermatological features (skin lesions), only muscle weakness and myalgia
Symptoms of dermatomyositis
Symmetrical, proximal muscle weakness
Myalgia
Muscle wasting
Raynaud’s
Skin involvement
Other organ involvement (lungs, oesophagus, heart)
Fever
What will patients complain of if they have dermatomyositis
Difficulty combing hair
Difficulty walking up the stairs
Difficulty rising from a chair
Difficulty raising objects
What are the skin features of dermatomyositis
Heliotrope rash
Gottron’s papules
Shawl rash - across back and shoulders
Very dry and scaly hands
Nail fold erythema
Where is heliotrope rash seen
Purple rash on eyelids
Where are Gottron’s papules seen
red papules on the dorsal aspect of the finger joints
In dermatomyositis
What are the other organ involvement of dermatomyositis
Lung
- respiratory muscle weakness
- Interstitial lung disease
Oesophagus
- dysphagia
Heart
- myocarditis
Investigations for dermatomyositis
- Creatine kinase level (raised)
Muscle biopsy
auto-antibody screen
Autoantibodies specific to dermatomyositis
Anti-Jo1
Anti-SRP
What are the non-specific autoantibodies that can present in dermatomyositis but also other conditions
Anti-Mi2
Anti-RNP
Management of dermatomyositis
Oral steroids (prednisolone)
Screen for malignancy (because it is associated with malignancy)
Which steroid is used for dermatomyositis
Prednisolone
What is the most common chronic MSK pain in women 20-40 years old
Fibromyalgia
What is fibromyalgia
Neurosensory disorder characterised by chronic MSK pain
Risk factors of fibromyalgia
Women
20-40
Family history
Fibromyalgia is associated with which other conditions
RA (seen in 25% of patients with RA)
SLE (seen in 50% of patients with SLE)
Cause of fibromyalgia
disorder of central pain processing causing lower threshold of pain and of other stimuli, amplifying pain
Symptoms of fibromyalgia
Persistent widespread pain
Fatigue (due to disrupted sleep cuz of pain)
Headaches
Anxiety, Depression
Non-cardiac chest pain
What is considered as widespread pain
Pain in
- both sides of the body
- above and below the waist
- including axial spine
What clinical findings may be present in fibromyalgia
at least 11 out of 18 tender points on palpation
Pain on palpating those tender points
Where are the 18 possible tender points of fibromyalgia
Around the lower neck
Hips
Shoulder
Upper back
Outer knee
Elbows
Investigations for fibromyalgia
Clinical
- patient experiencing widespread persistent pain and associated symptoms
- Symptoms present for >3m
- no other explanation of the pain
Management for fibromyalgia
Antidepressants (tricyclics)
Analgesia (tricyclics, gabapentin and pregabalin)
CBT
Exercise programmes and relaxation techniques
Which tricyclic is used for analgesia for fibromyalgia
Amitryptyline
What analgesia are used for fibromyalgia
Amitryptyline
Gabapentin
Pregabalin
What is myasthenia gravis
Autoimmune neurological disorder causing muscular weakness and progressive fatigue
Causes of myasthenia gravis
Autoantibodies against acetylcholine receptors limits the ability of acetylcholine to cause muscle contraction
Risk factors of myasthenia gravis
Women
60-70
Conditions associated with myasthenia gravis
SLE
RA
thyrotoxicosis
Thymic hyperplasia (in 50-70% of patients)
Thymoma
Symptoms of myasthenia gravis
Progressive muscular weakness
Progressive muscular fatigues
Drooping eyelids
Diplopia
Change in speech or swallowing
Difficulty in swallowing
Difficulty in smiling
Which muscles are often affected first in myasthenia gravis
Eyes
Face
Mouth
Throat
Which muscles are not commonly affected by MG
Neck
shoulder
Hip flexors
What are the hip flexor muscles
Psoas
Iliacus
Rectus femoris
Pectineus
Sartorius
Why may MG become life-threatening
Due to involvement of respiratory muscles causing impaired respiration
Investigations for MG
Clinical
Autoantibodies in blood
Imaging
What clinical findings may be seen in MG
Bilateral ptosis (drooping eyelids)
Difficulty speaking
Myasthenic snarl
What autoantibodies is found in blood tests for MG? Is it specific and sensitive?
Anti-ACHr (acetycholine receptor antibodies)
Yes it is both specific and sensitive (present in 90% of patients and 99% of those who have it have MG)
Why should imaging be done for MG
Because MG is associated with thymoma and thymus hyperplasia
Management of MG
- Anticholinesterase
- Steroids
- Surgery - thymectomy if associated with thymoma
Examples of anti cholinesterase
pyridostigmine
neostigmine
Use of anticholinesterase
inhibit the breakdown of acetylcholine in the synaptic cleft so increase activation of the receptors
Side effects of anti cholinesterase
diarrhoea
salivation
lacrimation
urinary frequency
Which steroid is used first line for MG
Prednisolone
What is myonecrosis
Life-threatening necrotizing soft tissue infection
Cause of myonecrosis
Clostridium perfringens from a contaminated wound
Symptoms of myonecrosis
- Disproportionate muscle pain
- Massive edema with skin discoloration that progresses from bronze to red-purple to black and overlying bullae
- Can progress to systemic infection
Progression of cutaneous manifestation of myonecrosis
Skin discolouration that changes colour from bronze -> red purple -> black + bullae
Investigations for myonecrosis
Imaging
Wound culture / blood culture
What would imaging show in myonecrosis
Feathering pattern
Management of myonecrosis
Immediate surgical debridement
Antibiotics
What is pyomyositis
Acute intramuscular infection secondary to haematogenous spread of the microorganism
Risk factors of pyomyositis
Person who inject drugs
Diabetes
Immunosuppressed
Most common causative pathogen of pyomyositis
S aureus
Pyomyositis in immunosuppressed patients is most commonly caused by
Pseudomonas
Beta haemolytic strep
Enterococcus
Pyomyositis in tropical climates is mostly caused by
MSSA (Meticillin sensitive S aureus)
Symptoms of pyomyositis
Pain
Swelling
Fever
Abscess in muscle
Investigations for pyomyositis
CT / MRI
Pus discharge culture
Management for pyomyositis
Surgical debridement, drain the pus
Antibiotics
Causative pathogens of viral myositis
Influenza
HIV
CMV
Rabies
Dengue
Presentation of viral myositis
Fever
Pain
tenderness
Weakness
Swelling
Investigations for viral myositis
Blood tests - show elevated creatinine kinase
Cause of tetanus
Clostridium tetani
Pathophysiology of tetanus
- C. tetani release neurotoxins
- the toxins bind to inhibitory neurons
- and prevents release of inhibitory neurotransmitters
- which causes widespread activation of motor neurons and spasming of muscles
Symptoms of tetanus
Trismus (lock jaw)
Risus sardonicus
Muscular spasms
Dysphagia
what is risus sarconicus
abnormal, sustained spasm of the facial muscles that appears to produce grinning
Complications of tetanus
laryngospasm (causing asphyxia)
respiratory failure
Investigations for tetanus
Clinical
Culture if not sure
Management for tetanus
IV tetanus immunoglobulin (antitoxin)
Supportive
Prevention of tetanus
Vaccination
Wound management
