Infectious Disease Case 2

Question 1

In the case with the girl who was diagnosed with mono and then her knee started hurting, what would be the diagnosis (not the cause yet)?

Answer 1

Acute monoarticular arthritis

meaning an acute joint inflammation that occurs days or less before seeking attention - just one joint

Question 2

What should be in the differential for acute monoarticular arthritis?

Answer 2

gout

pseudogout

reactive arthritis

septic arthritis

Question 3

What causes gout?

Answer 3

uric acid crystals precipitate in joint

Question 4

where is gout most common?

Answer 4

great toe, but knees and ankles common as well.

usually not the upper extremities

Question 5

How does one diagnose gout?

Answer 5

blood uric acid may not be elevated in an acute episode of gout, so it’s not actually diagnostic

do a joint aspiration and visualize under polarized light - you’ll negatively birefringent crystals

Question 6

What causes pseudogout?

Answer 6

instead of uric acid, it’s calcium pyrophosphate crystal deposition

Question 7

What joints does pseudogout tend to affect?

Answer 7

same joints as gout (toes, knees, wrist, ankles), plus the shoulders and hips

Question 8

How does one diagnose pseudogout?

Answer 8

joint aspiration will show positive birefringent crystals

Question 9

What does reactive arthritis follow?

Answer 9

urethritis from chlamydia

or

gastroenteritis

(usually about six weeks after the infection cleared)

Question 10

What joint is most commonly affected by reactive arthritis?

Answer 10

joints of the leg - knee in particular

Question 11

If the reactive arthritis is combined with conjunctivitis and urethritis, what syndrome is it?

Answer 11

Reiter syndrome

Question 12

What are the 2 most common microorganisms for septic arthritis?

Answer 12

staph aureus

neisseris gonorrhoeae

Question 13

Staph auerus is usually the most common cause of septic arthritis overall, but in what population is neisseria gonorrhoeae the most common?

Answer 13

sexually active individuals under age 30

Question 14

What are the two musculoskeletal syndromes caused by disseminated gonorrhoeae?

Answer 14

1. arthritis-dermatitis syndrome
2. localized septic arthritis

Question 15

What happens in arthritis-dermatitis syndrome?

Answer 15

arthralgias

skin lesions

inflammation of tendons

NOTE: the septic arthritis is rarely found at the same time as the bacteremia (that comes first)

Question 16

WHat happens in localized septic arthritis?

Answer 16

it’s localized to one joint - usually the knee

the bacteremia comes first and then the arthritis develops after the bacteremia resolves

No skin lesions…

Question 17

Which phenotypes of gonococci are more likely to disseminate? When do they?

Answer 17

The phenotyes that are expressed during menstruation are more likely to disseminate, one week after the start of menses

Question 18

Is GC more or less likely to disseminate in homosexual men?

Answer 18

less likely

Question 19

True or false: strains that disseminate are more potent stimulators of inflammatory responses and are therefore likely to cuase urethral symptoms.

Answer 19

False - they are less potent stimulators of inflammatory responses, so the patient often wouldn’t know they were infected until the joint aspiration came back showing GC

Question 20

What would show up on labs in GC septic arthritis?

Answer 20

WBC elevated

Blood cultures frequently positive

joint aspiration will show hugely elevated WBC< but that’s not specific since it can also be seen in gout

gram stain and culture of joint aspiration is the primary diagnostic test

Question 21

What will a GC joint infection look like on gram stain?

Answer 21

gram negative diplococci

(plus lots of PMNs)

Question 22

What is the treatment for a GC septic arthritis? Does it clear easily?

Answer 22

You treat with injection ceftriazone and oten an oral macrolide like azithromycin (which would also work for presumptive treatment of chlamydia)

prognosis is very good - they get better quickly