Muscle Pathology -Parsa Flashcards
What is the difference between neurogenic and myopathic pathology of muscles?
- neurogenic: due to interruption from the CNS (UMN or LMN lesions). will show type grouping (fast bundled separate from slow).
- myopathic: normal nerves, scattered myocytes are smaller (not grouped–> type I and II both atrophy). problems due to the mm fibers
What are some findings seen in the lower extremity in Duchennes muscular dystrophy? What will the CK be in the late stages of this?
- pseudohypertrophy of the calves–> initial increase in mm fiber size (both type 1 and 2 involved)
late: mm replaced by fat and CT
CK will be normal because NO more mm to destroy
What does the pathogenesis of Dermatoyositis involve? What does it look like clinically?
- B & T cells, mostly CD4+helper located predominantly around small blood vessels and in the perimysial connective tissue
- perimysium inflamed and peripheral fibers atrophied
- capillary walls have MAC (membrane attack complex)–> vascular injury and fibrosis –> ischemic myocytes
-elevated CK, heliotrope rash, gottron papules over knuckles, high risk for cancer!
What is inclusion body myositis?
- autoimmune similar to polymyositis but with rimmed vacuoles (lysosomes) (below)
- CD 8+ cytotoxic T lymphocytes
- β-amyloid & tau protein inclusions
- begins with distal mm involvement (knee, wrist and fingers)
What myopathy is associated with malignant hyperthermia?
Central core disease
(a ryanodine receptor mutation)
Ca2+ channel protein
What should be suspected in a young person presenting with stroke and muscle pain?
mitochondrial disease
–> biopsy to confirm
How does a pt with mitochondrial disease typically present?
in young adulthood
- proximal mm weakness
- sometimes severe involvement of the extraoccular mm.
-can be accompanied by: neurologic (stroke-like) symptoms, lactic acidosis and cardiomyopathy
–> distortion of the myofibrils–> ragged red fibers in cross-section
- paracrystalline mitochondrial inclusions (parked car appearance)
- lack staining for cytochrome oxidase (electron transport carrier normally encoded in mtDNA)
What is myotonic dystrophy? How does it present and what causes it?
-squeeze hand and can’t let go!!
(Na+ channel problem)
- muscle atrophy with abnormal gait, cataracts, frontal baldness, testicular atrophy, heart disease, low intelligence
- autosomal dominant trait
- CTG repeat on chromosome 19–> affects dystrophia myotonia protein kinase (DMPK) –> may have a role in the normal function of skeletal muscle Na+ channels.
- variation in fiber size, ring fiber, increase in internal nuclei
- heart: fibrosis of conducting system, myocyte hypertrophy and fatty infiltration
What cancer is related to Myasthenia gravis?
Thymoma
CT the chest to make sure no thymoma
-autoimmune against post synaptic AChRs (EMG worsen with activity)
What cancer is associated with Lambert-Eaton syndrome?
Small cell lung cancer
-presynaptic ACh inhibited (EMG will improve with activity)
At what age is embryonal rhabdymyosarcoma likely to form and where?
Alveolar rhabdomyosarcoma?
Pleomorphic rhabdymyosarcoma?
Embryonal rhabdomyosarcoma: head and neck of children (strap and racquet shaped cells) (botryoids is a subset-> soft, multilobular, polypoid mass develops in the walls of hollow, mucosal-lined structures–> bladder and uterus)
Alveolar rhabdomyosarcoma: early to middle adolescence and deep in musculature of extremities
Pleomorphic: > 45 yo extremities
A 4-year-old boy is brought to a pediatrician by his parents who complain of the child’s delayed clumsy walking discordant with his chronological age. They also complain of the child’s inability to keep up with his peers’ other motor skills.
According to the mother, a male cousin on her side of the family was afflicted with a similar condition.
Physical examination reveals enlargement of the calf muscles.
Needle biopsy of the calf muscle was performed and submitted for pathologic examination. What is the differential?
Duchenne / Becker muscular dystrophy
What will the CK be for the first decade of life in a pt with Duchennes? after the first decade?
first decade: elevation in CK
late: normal as mm mass decreases
A retired 73-year-old man, is admitted to hospital with the chief complaint of increasing weakness in his hands and shoulders such that he finds it hard to lift his arms above his head.
Administration of a short-acting anticholinesterase drug has no benefit on his muscle strength.
On examination he has moderate weakness in the shoulder and pelvic girdle muscles. Investigations show a normal full blood count and ESR. His serum creatine kinase shows a slight elevation above normal.
What is the likely diagnosis?
Inclusion-body myositis is clinically similar to polymyositis but occurs mainly in elderly patients.
A 25-year-old male presents to the emergency department complaining of excruciating pain in his lower extremities following an attempt at a marathon run which was abruptly terminated because of the pain. Laboratory tests revealed an elevated serum creatin kinase and a discordantly low serum lactate acid level. The patient’s urine is dark brown.
McArdle Disease
(Myophosphorylase Deficiency)
inability to generate
lactate with exercise
(defect in anaerobic
glycogen metabolism)
- accumulation of PAS-+ glycogen and empty glycogen vacuoles
- presents w: Painful cramps associated with strenuous exercise; myoglobinuria occurs in 50% of cases; onset in adulthood (>20 years); muscular exercise fails to raise lactate level in venous blood; serum creatine kinase always elevated; compatible with normal longevity.
