muscle disease Flashcards
what is a marker of muscle fibre damage and increases greatly in many dystrophies
creatinine kinase
what medically can cause myopathies
corticosteroids and cushings (proximal weakness), thyrotoxicosis, calcium, hypokalaemia
what are the inflammatory myopathies
polymyositis, dermatomyositis- skin also involved- heliotrope rash and Gottrons papules
what is myotonic dystrophy
autosomal dominant. expanded CTG repeat in protein kinase DMPK.
what are the features of myotonic dystrophy
progressive DISTAL weakness, ptosis, thinning and weakness of face and sternomastoids
what is myotonia
typically present in myotonic dystrophy and is the inability to relax voluntary muscle after vigorous effort
what is muscle disease part of a syndrome with in myotonic dystrophy
cataracts, frontal balding, cognitive impairment, oesophageal dysfunction, cardiomyopathy, impaired glucose tolerance, hypogonadism
what can be used to relieve the myotonia
phenytoin or procainamide
how is Duchenne/Beckers inherited
X linked recessive, although 1/3 are spontaneous mutations
what is absent in DMD
dystrophin which is essential for cell membrane stability and so there are reduction of 3 glycoproteins in the DAP complex
what happens in Beckers
dystrophin is present but low levels. less severe than Duchennes, weakness only becomes apparent in adults
clinical features DMD
usually obvious by age 4. difficulty running and rising to his feet. Gowers sign. Pseudohypertrophy of the calves and proximal limb weakness. myocardium affected
investigations in DMD
CK is grossly elevated. biopsy- muscle fibre size, necrosis, replacement by fat
what is a females chance of being a carrier if she has a brother with it
50% of carrying DMD gene
