UWorld-Musculoskeletal

Question 1

comedonal and inflammatory nodular eruptions (acne) can be caused by what substances

Answer 1

methyltestosterone (anabolic steroids), epidermal growth factor receptor inhibitors, and lithium

Question 2

what conditions does chewing tobacco predispose to

Answer 2

dental carries, gingivitis, oral leukoplakia, oral cancer

Question 3

how do anabolic steroids cause acne

Answer 3

anabolic steroids (methyltestosterone) causes epidermal hyperproliferation and sebum overproduction

Question 4

verruca vulgaris is caused by what strains of what pathogen

Answer 4

HPV strains 1-4

Question 5

a patient with migratory joint pain, a malar rash and generalized LAD has a disease that can involve defective Fas receptor; what does this receptor do

Answer 5

Fas receptor, when bound to Fas ligand causes apoptosis

Question 6

an increase in PRPP synthetase activity could cause what condition

Answer 6

hyperuricemia leading to gout

Question 7

which kind of cell is most responsible for the pain and swelling seen in gout

Answer 7

neutrophils

Question 8

a patient with pain shooting down the posterior thigh and posterior leg likely has what condition?
what are the possible nerve roots involved and which nerve root would cause impaired ankle jerk reflex?

Answer 8

sciatica;
sciatica is caused by impingement of the sciatic nerve

S1 is responsible for ankle jerk reflex (plantar flexion)

Question 9

osteocytes are connected to each other by what kind of intercellular connector

Answer 9

gap junctions

Question 10

a baby with lethargy, poor feeding, jaundice, constipation, muscle hypotonia, macroglossia and umbilical hernia

Answer 10

congenital hypothyroidism

Question 11

what respiratory complication is seen in ankylosing spondylitis and why;
what must you monitor in these patients regarding this complication

Answer 11

enthesitis (inflammation of tendon insertion) causes pain upon respiration at the costovertebral and costosternal angles leading to hypoventilation so chest expansion must be monitored in these patients

Question 12

what does osteoprotegerin (OPG) do and where does it come from

Answer 12

OPG is secreted by osteoblasts as a decoy for RANK receptor;

OPG binds RANK ligand, preventing it from binding the receptor on osteoclasts and thereby inhibiting bone resorption

Question 13

late separation of the umbilical cord suggests what condition;
what’s the defect

Answer 13

leukocyte adhesion deficiency;

caused by deficient CD18, which is needed for formation of integrins

Question 14

the cell is permeable to what two ions

Answer 14

K+ and slightly permeable to Na+

Question 15

how do you differentiate between septic arthritis and gout/pseudogout for an acute monoarticular arthritis

Answer 15

WBC > 20,000 is septic arthritis

WBC < 20,000 is gout/pseudogout

Question 16

hematogenous osteomyelitis tends to occur in what population?
what part of the bone?

Answer 16

children (often boys);

long bone metaphysis

Question 17

what is the cause of myasthenia gravis

Answer 17

autoantibodies to post-synaptic nicotinic ACh receptors which bind and cause internalization and complement-mediated degradation of the receptors

Question 18

what happens at the pre-synaptic membrane vs. the post-synaptic membrane in myasthenia gravis

Answer 18

pre-synaptic membrane is unaffected (ACh concentration is normal)
post-synaptic nicotinic ion channels don’t open –> reduced end plate potential

Question 19

which muscles are most commonly affected by myasthenia gravis

Answer 19

muscles innervated by cranial motor nuclei (facial, ocular, hypoglossal, masticatory muscles)

Question 20

probenecid and sulfinpyrazone treat what condition

Answer 20

they are uricosuric drugs that are used for long-term management of gout

Question 21

name a diuretic that increases serum Ca2+

name a diuretic that decreases serum Ca2+

Answer 21

hydrochlorothiazide increases DCT reabsorption of Ca2+

furosemide causes Ca2+ wasting

Question 22

Grotton papules (red/violaceous, flat-topped papules over bony prominences) and heliotrope rash (red/violaceous, edematous eruption on upper eyelids or periorbital skin) suggests what condition

Answer 22

dermatomyositis (also associated with proximal muscle weakness and anti-Jo1 antibodies, which are a specific marker)

Question 23

keratoderma blenorrhagicum (vesiculo-pustular desquamating rash of yellow/brown appearance) and sacroilitis are common, but not pathognomonic features of

Answer 23

reactive arthritis

Question 24

common cause of demineralized bone (osteoid)

Answer 24

vitamin D deficiency

Question 25

anti-DNA topoisomerase I antibodies are specific for

Answer 25

systemic sclerosis (aka diffuse scleroderma)

Question 26

side effects of colchicine

Answer 26

nausea, abdominal pain, diarrhea

Question 27

what is haptoglobin and what does an abnormal value tell you

Answer 27

haptoglobin binds free hemoglobin to prevent its renal excretion;
in intravascular hemolysis haptoglobin-hemoglobin complexes will be hepatically cleared –> lower haptoglobin levels
in extravascular hemolysis the macrophages clear the hemoglobin in the cells they destroy so haptoglobin remains unchanged

Question 28

name the most common injury in young children

Answer 28

radial head subluxation (nursemaid’s elbow), which involves displacement of the annular ligament that normally holds the radius in place

Question 29

list the three parts of the “female athelete triad” associated with anorexia nervosa

Answer 29

eating disorder, amenorrhea, osteoporosis

Question 30

prolonged kneeling causes injury to which bursa

Answer 30

prepatellar bursitis (“housemaids knee”)