Muscle Disorders Flashcards
What are muscular dystrophies and how do you Rx
Inherited muscle disorders that cause progressive weakness
Steroids
Ataluren - new drug which restores synthesis of dystrophin
OT / Physio
Treat other conditions
What should you think if rapid onset
Toxins
Drugs e.g. statin
Metabolic
What is Duchenne’s
X-linked recessive
Problem with dystrophin protein in muscle
Xp21 gene
Short survival
What are the symptoms of muscular dystrophies
What are later signs
Proximal muscle weakness first - shoulder / girdle
Muscle wasting
Pseudohypertrophy due to fatty infiltration of muscle
Gowers +ve (use hands on legs to help stand)
Waddling gait
Intellectular impairment
FTT
Late signs SOB due to resp muscle weakness Dysphagia Cardiomyoapthy + arrhythmia - screen Myoglobulinuria Scoliosis Tendon contractures Reduced tone and reflexes = late
What is Becker’s and how is it inherited
Milder form of DMD
X-linked
What is fascioscapulohumeral and how is it inherited
Facial, scapular and biceps weakness Weakened diaphragm Bilateral sensorineural hearing loss Retinal telangiectasis AD
What is limb girdle dystrophy
Upper and LL proximal weakness
How do you differentiate myopathy from neuropathy
More gradual onset Proximal weakness Specific muscle groups Preserved reflex No parathesia or bladder No fasiculations
What is myotonic dystrophy and what process does it follow and how do you Dx
Inherited AD affecting skeletal, cardiac and smooth muscle
Trinucleotide repeat disorder - anticipation
Most common muscle disease to present in adulthood
Dx = genetic analysis
What does it cause
Progressive muscle weakness
Prolonged contraction and unable to relax e.g. when shaking hand can’t let go
Cataract
Heart conduction - Cardiac arrhythmia / cardiomyopathy / heart block
Infertility due to testicular atrophy
Intellectual impairment
Peripheral neuropathy
Myotonic facies - ptosis / can't close mouth Frontal balding Bilateral ptosis Dysarthria Myotonia DM - type II Dysphagia
What are channelopathies
Abnormal fluxes of Ca, Na and Cl
Familial hypokalaemia periodic paralysis
Hyperkalaemia paralysis
Paramyotonia congenital
What are Sx
Episodic intermittent Sx
Unusual muscle contraction
Profound weakness
Measure K
What are metabolic muscle disorders
Disorders of carb / lipid metabolism
Mitochondria myopathy
Endocrinopathy
More significant weakness on exertion
What drugs can cause myopathy
Statins
Alcohol
Steroids
What are inflammatory muscle disease and what do they tend to have
Polymyositis - CD8
Dermatomyositites - CD4
Spontaneous pain at rest and local tenderness
What are the SX
Painful weak muscles Shoulder and pelvic girdle Dysphagia Resp Characteristic rash - heliotrope vs gottron's papule
What do you do for all muscle disorders including inerhited
Bloods - CK, ESR, AST and LDH - usually elevated EMG Muscle Biopsy Genetic test
How do you Rx
Steroids
Immunosuppresion
What is myasthenia gravis
Disorder of NMJ due to insufficient functioning Ach receptor
Ab against Ach receptor on post synaptic side of NMJ
Autoimmune
What causes exacerbation
Exertion BB Lithium Phenytoin Ax Pregnancy Infecion Hypokalaemia
What are the Sx
Fatigable weakness in
Limbs
Ptosis at end of the day (droopy eyelid)
- Worsened prolonged upgaze
Extra-ocular muscle - diplopia
Proximal muscle wasting
Facial and bulbar weakness
- Dysphagia
- Weakness in muscles of mastication / speech
SOB due to weakness in resp muscles = dangerous
- Can go into type 2 resp failure
What are associations
Thymonas (20%) Pernicious anaemia Autoimmune thyroid Rheumatoid SLE
How do you Dx
AchR Ab = 80% Anti-MuSk Ab / tyrosine kinase Ab if -ve Neurophysiology / EMJ - Decreased response to stimulation CT chest to look for thymoma CK normal Spirometry to check FVC
How do you Rx
Long acting acetylcholinesterase inhibitor - pyridostigmine Immunosuppression - Initially prednisone if doesn't help - Azathioprine Bone protection if on steroid Thymectomy even if no thymoma
