Muscle diseases Flashcards by Cathy Wang

What is dermatomyositis

inflammatory disorder causing symmetrical, proximal muscle weakness and characteristic skin lesions

How well did you know this?

Not at all

Perfectly

Cause of dermatomyositis

Idiopathic
Associated with other connective tissue disorders or malignancy

How well did you know this?

Not at all

Perfectly

What malignant conditions are associated with dermatomyositis

ovarian cancer
breast cancer
lung cancer

How well did you know this?

Not at all

Perfectly

What is polymyositis

A variant of dermatomyositis but without dermatological features (skin lesions), only muscle weakness and myalgia

How well did you know this?

Not at all

Perfectly

Symptoms of dermatomyositis

Symmetrical, proximal muscle weakness
Myalgia
Muscle wasting
Raynaud’s
Skin involvement
Other organ involvement (lungs, oesophagus, heart)
Fever

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Where is heliotrope rash seen

Purple rash on eyelids

How well did you know this?

Not at all

Perfectly

Where are Gottron’s papules seen

red papules on the dorsal aspect of the finger joints
In dermatomyositis

How well did you know this?

Not at all

Perfectly

What are the other organ involvement of dermatomyositis

Lung
- respiratory muscle weakness
- Interstitial lung disease
Oesophagus
- dysphagia
Heart
- myocarditis

How well did you know this?

Not at all

Perfectly

Investigations for dermatomyositis

Creatine kinase level (raised)
Muscle biopsy
auto-antibody screen

How well did you know this?

Not at all

Perfectly

Autoantibodies specific to dermatomyositis

Anti-Jo1
Anti-SRP

How well did you know this?

Not at all

Perfectly

What are the non-specific autoantibodies that can present in dermatomyositis but also other conditions

Anti-Mi2
Anti-RNP

How well did you know this?

Not at all

Perfectly

Management of dermatomyositis

Oral steroids (prednisolone)
Screen for malignancy (because it is associated with malignancy)

How well did you know this?

Not at all

Perfectly

Which steroid is used for dermatomyositis

Prednisolone

How well did you know this?

Not at all

Perfectly

What is the most common chronic MSK pain in women 20-40 years old

Fibromyalgia

How well did you know this?

Not at all

Perfectly

What is fibromyalgia

Neurosensory disorder characterised by chronic MSK pain

How well did you know this?

Not at all

Perfectly

Risk factors of fibromyalgia

Women
20-40
Family history

How well did you know this?

Not at all

Perfectly

Fibromyalgia is associated with which other conditions

RA (seen in 25% of patients with RA)
SLE (seen in 50% of patients with SLE)

How well did you know this?

Not at all

Perfectly

Cause of fibromyalgia

disorder of central pain processing causing lower threshold of pain and of other stimuli, amplifying pain

How well did you know this?

Not at all

Perfectly

Symptoms of fibromyalgia

Persistent widespread pain
Fatigue (due to disrupted sleep cuz of pain)
Headaches
Anxiety, Depression
Non-cardiac chest pain

How well did you know this?

Not at all

Perfectly

What is considered as widespread pain

Pain in
- both sides of the body
- above and below the waist
- including axial spine

How well did you know this?

Not at all

Perfectly

What clinical findings may be present in fibromyalgia

at least 11 out of 18 tender points on palpation
Pain on palpating those tender points

How well did you know this?

Not at all

Perfectly

Where are the 18 possible tender points of fibromyalgia

Around the lower neck
Hips
Shoulder
Upper back
Outer knee
Elbows

How well did you know this?

Not at all

Perfectly

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

1. Anticholinesterase 2. Steroids 3. 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

1. C. tetani release neurotoxins 2. the toxins bind to inhibitory neurons 3. and prevents release of inhibitory neurotransmitters 4. 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