Diseases of Muscle Flashcards by kat remigio

T/F

Eye muscles do not contain dystrophin.

True

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Normal muscle is endowed with a population of embryonic muscle precursor cells known as _______ cells and as a result, it possesses a remarkable capacity to regenerate.

satellite cells

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Muscle connective tissue derives from the

somatopleural mesoderm

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At all ages, disuse of muscle decreases fiber size by a smuch as ____ percent and overuse increases the size by about the same amount.

30%

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6 Grades of Muscle strength by the Medical Research Council of GB

0 complete paralysis
1 minimal contraction
2 active movement only with gravity eliminated
3 full movement against gravity but cannot offer resistance to manual muscle opposition
4 active movement against gravity and resistance but can be overcome by manual muscle opposition
5 normal strength

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stiffness and slowness of contraction in a muscle such as the quadriceps may be seen on change in postures

contraction myoedema

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prolonged failure of relaxation, following contraction of a muscle is characteristic of

myotonia

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T/F

Pain tends to be prominent in polymyositis and dermatomyositis.

False

pain tends NOT to be prominent but there are exceptions
p1411

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T/F

As a general rule, muscle diseases are identified by a predominantly proximal weakness that is symmetric.

true

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T/F

When weakness of the orbicularis oculi (muscles of eye closure) is added to weakness of eye opening (levator palpebrae; ptosis), it nearly always signifies myasthenia gravis and occasionally, a rare primary disease of muscle (progressive external ophthalmoplegia [PEO]).

true

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T/F

Paradoxical inward movement of the abdomen with inspiration is another sign of diaphragm weakness.

True

p1414

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Most common pattern of a number of myopathies.

most often, polymyositis, IBM, dermatomyositis, and the muscular dystrophies present in this fashion

Proximal Limb-Girdle palsies presenting as inability to raise arms or to arise from a squatting, kneeling or sitting position

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weakness of IBM has a preference for certain sites

quadriceps or of the forearm muscles particularly the long finger flexors

flexor digitorum profundus

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parasitic disease
ocular muscle weakness, causes strabismus and diplopia
tongue weakness -> dysarthria
weakness of masseter and pharyngeal muscles - diff chewing and swallowing
weakness of limb muscles proxima>distal
conjunctival, orbital, facial edema
subconjunctival, subungual splinter hemorrhages

dx: puffy face with tender muscles
eosinophilia >700
ELISA is accurate but positive only after 2 weeks of illness
biopsy is the most reliable confirmatory test
biopsy: segmental necrosis, interstitial inflammatory infiltrates, eosinophils

Trichinosis

caused by nematode Trichinella spiralis

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treatment for Trichinosis

no treatment in most cases
severe weakness and pain: thiabendazole 25-50mg/kg daily in divided doses for 5-10 days
prednisone 40-60mg/kg per day
albendazo,e 400mg OD

recovery is complete
except in pts with infarcts

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In the AIDS population, myositis from toxoplasma is more common than brain infestation

False
p1416

brain infestation more common

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treatment for toxoplasmosis myositis

sulfadiazine in combi with pyrimethamine or trisulfapyrimidine
folic acid is given in addition

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an antiretroviral drug used to treat HIV, may induce a myopathy with myalgia and weakness that is indistinguishable from HIV myopathy

zidovudine

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T/F

The clinical features of putative ZVD-induced myopathy are much the same as those of HIV myopathy except that moderate pain is said to be characteristic of the druginduced variety

True

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T/F

The myopathologic changes in AIDS are also like those of idiopathic polymyositis.

true

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idiopathic subacute or chronic symmetrical weakness of proximal limb and trunk muscles without dermatitis

Polymyositis

insidious, course progressive several weeks to months
febrile illness or benign infection may precede the weakness
painless weakness

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T/F

Ocular muscles are not affected in PM.

True

but there are rare instances of combined PM and MG

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denominative feature is rash
most often, the skin changes precede the muscle syndrome
localized or diffuse erythema, maculopapular eruption, scaling eczematoid dermatitis, exfoliative dermatitis
prominent in childhood DM: Gottron papules
heliotrope
V sign and shawl sign

Dermatomyositis

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T/F

Serum CK levels tend to be higher in PM than in DM.

true

because of the widespread single-fiber necrosis in the former. however in DM if there are infarcts in muscle, CK levels will be moderately elevated as well
ESR is normal or mildly elevated

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T/F Absent or low titer ANA and normal ESR do not exclude the diagnosis of PM.

true

T/F When performing EMG and biopsy, perform the needle examination and biopsy on the same side and site.

False p1421 EMG on one side and biopsy on the other side

pathologic changes in idiopathic PM

widespread destruction of segments of muscle fibers with an inflammatory reaction - phagocytosis of muscle fibers by mononuclear cells and infiltration with a varying number of lymphocytes and lesser number of other mononuclear or plasma cells

characteristic pathologic changes in Dermatomyositis

perifascicular muscle fiber atrophy others: inflammatory infiltrates in DM predominate in perimysial connective tissue, in PM: most prominent in relation to the muscle fiber membrane and endomysium

distinctive microvascular changes in muscle in dermatomyositis

``` endothelial alterations (tubular aggregates in the endothelial cytoplasm) occlusion of vessels by fibrin thrombi ```

in Dermatomyositis, what are deposited in the walls of venules and arterioles indicating that immune response is directed primarily against intramuscular blood vessels

immune complexes, IgG, IgM, C3 and membrane attack complexes

In Polymyositis, there are a large number of _____ cells. In Dermatomyositis, there are a larger number of _____ cells.

PM - activated T cells - cytotoxic | DM - B cells - humoral

treatment for PM and DM

corticosteroids prednisone 1mg/kg as a single daily dose orally or IV acute and severe case, high dose methylprednisolone 1g infused over 2 hours each day for 3-5 days

monitoring parameters in DM and PM treatment

muscle strength and serum CK measurement

T/F DM and PM treatment. In patients who respond, the serum CK decreased before the weakness subsides and with relapse, the serum CK rises before weakness returns.

True

when to give IVIg in DM

when patients responds poorly to steroids and other immunosuppressants or are severely affected early on, several courses of treatment at monthly intervals may be required to achieve sustained improvement

Other immunosuppresants for PM and DM

``` azathioprine methotrexate cyclophosphamide rituximab cyclosporine mycophenolate mofetil ```

Prognosis in PM and DM

generally favorable except for patients with malignancy

most common inflammatory myopathy in patients older than 50 years

inclusion body myositis

Defining features of IBM

intracytoplasmi and intranuclear inclusion

T/F in IBM. Associations with malignancy or systemic autoimmune disease have been established.

False Have NOT been established

weakness presentation in IBM

more focal than PM and DM steadily progressive painless muscular weakness and modest atrophy weakness: distal in arms and both proximal and distal in legs focal weakness of quadriceps, finger or wrist flexors, or lower leg muscles on one or both sides selective weakness of flexor pollicis longus is a particularly characteristic pattern of involvement

Lab/diagostic features in IBM serum CK EMG biopsy

serum CK is normal or slightly elevated - generally loer levels than in PM EMG - same i PM, myopathic pattern but in a proportion may show neuropathic pattern biopsy - intracytoplasmic, subsarcolemmal vacuoles and eosinophilic inclusions in both the cytoplasm and nuclei of degenerating muscle fibers (Gomori trichome in frozen sections) rimmed vacuoles

Treatment for IBM

IBM has not responded in any consistent fashion to treatment with corticosteroids or other immunosuppressive drugs

greatly thickened fascia, extending from the subcutaneous tissue to the muscle and infiltrated with plasma cells, lymphocytes, and many eosinophils ages of 30 and 60 years and are often precipitated by heavy exercise low grade fever and myalgia followed by the subacute development of diffuse cutaneous thickening and limitation of movement of small and large joints proximal muscle weakness and eosinophilic infiltration of muscle can be demonstrated

Eosinophilic Fasciitis

T/F Eosinophilic Fasciitis Repeated examinations of the blood disclose an eosinophilia in most but not all patients.

True

Treatment for Eosinophilic Fasciitis

Steroids

Painful swelling of a calf muscle or, less frequently, some other muscle has been the chief characteristic of this disorder. Biopsy discloses inflammatory necrosis and edema of the interstitial tissues; the infiltrates contain large but variable numbers of eosinophils The response to prednisone was dramatic; the swelling and pain subsided in 2 to 3 weeks and her power of contraction was then normal

Eosinophilic monomyositis

The features of the muscle disorder were typical of PM except that the inflammatory infiltration was predominantly eosinophilic and the muscles were swollen and painful. systemic manifestations include: eosinophilia, cardiac involvement, vascular disorder (Raynaud, subungual hemorrhages) pulmonary infiltrates, strokes, anemia, neuropathy, hypergammaglobulinemia.

Eosinophilic Polymyositis

A proportion of patients with Eosinophilic Polymyositis are attributable to mutations in

CAPN3 | gene for calpain-3

severe generalized myalgia and eosinophilia of the peripheral blood following the ingestion of contaminated L-tryptophan, onset of the muscular illness was relatively acute, with fatigue, low-grade fever, and eosinophilia (>1,000 cells /mm3) Muscle pain and tenderness, cramps, weakness, paresthesias of the extremities, and induration of the skin were the main clinical features. A severe axonal neuropathy with slow and incomplete recovery was associated in some cases

Eosinophilia-Myalgia Syndrome

most frequent and best known of the early-onset muscular dystrophies

Duchenne Muscular Dystrophy X-linked recessive, dystrophin gene

begins in early childhood and runs a relatively rapid, progressive course X-linked recessive trait rarely, a severe proximal Duchenne-type muscular dystrophy occurs in young girls- female may have only 1 X chromosome, as occurs in the Turner or or the Lyon principle may be operative; that is, there is inactivation of the unaffected paternal X chromosome allowing expression of the mutated Duchenne protein from the maternal chromosome in a large proportion of embryonic cells (mosaicism) usually recognized by the third year of life and almost always before the sixth year greatly elevated CK Increasing difficulty in walking, running, and climbing stairs, excessive lumbar lordosis, and waddling gait there may be pseudohypertrophy Gower sign The tendon reflexes are diminished and then lost as muscle fibers disappear

Duchenne Muscular Dystrophy

In duchenne MD, which muscles are affected that account for a lordotic posture and protuberant abdomen when standing and the rounded back when sitting

weakness of abdominal and paravertebral muscles

describe habitual posture of patient with DMD

lumbar lordosis, hip flexion and abduction, knee flexion, and plantar flexion

serum CK values in DMD

25 to 200 times normal

age of onset: mean 12yrs, range 5-45yrs X-linked not uncommon to walk well in adult life causes weakness and hypertrophy in muscles affected by a more severe X-linked recessive dystrophy

Becker Muscular Dystrophy

Pathology of Duchenne and Becker Dystrophies

early stages of Duchenne dystrophy: the most distinctive features are prominent segmental degeneration and phagocytosis of single muscle fibers or groups of fibers and evidence of regenerative activity

the protein dystrophin is express in what parts of the body

skeletal, cardiac, smooth muscles | brain

T/F Whereas dystrophin is absent in patients with the Becker phenotype, it is present but structurally abnormal in the Duchenne type.

False absent in Duchenne

T/F The dystrophin-glycoprotein complex functions in this scheme as a transsarcolemmal structural link between the subsarcolemmal cytoskeleton and the extracellular matrix.

True

X-linked muscular dystrophy deficiency in the protein emerin, a constituent of nuclear membrane Weakness affects first the upper arm and pectoral girdle musculature and later the pelvic girdle and the distal muscles in the lower extremities distinguishing feature of the disease is the early appearance of contractures in the flexors of the elbow, extensors of the neck, and posterior calf muscles. no hypertophy or pseudohypertrophy severe cardiomyopathy with variable sinoatrial and atrioventricular conduction defects is a common accompaniment

Emery-Dreifuss Muscular Dystrophy

slowly progressive dystrophy involving primarily the musculature of the face and shoulders, often with long periods of nearly complete arrest autosomal dominant age of onset 6-20 yrs first manifestations are difficulty in raising the arms above the head and winging of the scapulae, although bifacial weakness may have initially attracted attention, even in early childhood There is an inability to close the eyes firmly, to purse the lips, and to whistle; the lips have a peculiar looseness and tendency to protrude. The lower parts of the trapezius muscles and the sternal parts of the pectorals are almost invariably affected Usually the biceps waste less than the triceps, and the brachioradialis muscles even less, so that the upper arm may be thinner than the forearm ("Popeye" effect) An interesting feature of this group of diseases is the occasional congenital absence of a muscle (amyoplasia of one pectoral, brachioradialis, or biceps femoris) or part of a muscle in patients who later develop the typical features of the disease

Fascioscapulohumeral Muscular Dystrophy (Landouzy-Dejerine Muscular Dystropy) deletions in a repeated segment allow the expression of normally inactive genes such as DUX4.

slowly progressive myopathy primarily involving and often limited to the extraocular muscles. the levators of the eyelids are the first to be affected, causing ptosis, followed by progressive balanced ophthalmoparesis The eyelids are abnormally thin due to atrophy of the levator muscles. The orbicularis oculi muscles are frequently involved in addition to the extraocular muscles. The characteristic feature is that ptosis and ocular paralysis precede involvement of other muscles by many years.

Progressive External Ophthalmoplegia

T/F The pupillary responses and accommodation are normal in PEO.

True

Mutations in three nuclear genes in PEO have been implicated

twinkle, a mitochondrial DNA binding protein; ANT1 , an adenine nucleotide transporter in the intermembrane space in the mitochondrion; and POLG, a subunit of the mitochondrial DNA polymerase