Infectious Disease Case 2 Flashcards
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)?
Acute monoarticular arthritis
meaning an acute joint inflammation that occurs days or less before seeking attention - just one joint
What should be in the differential for acute monoarticular arthritis?
gout
pseudogout
reactive arthritis
septic arthritis
What causes gout?
uric acid crystals precipitate in joint
where is gout most common?
great toe, but knees and ankles common as well.
usually not the upper extremities
How does one diagnose gout?
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
What causes pseudogout?
instead of uric acid, it’s calcium pyrophosphate crystal deposition
What joints does pseudogout tend to affect?
same joints as gout (toes, knees, wrist, ankles), plus the shoulders and hips
How does one diagnose pseudogout?
joint aspiration will show positive birefringent crystals
What does reactive arthritis follow?
urethritis from chlamydia
or
gastroenteritis
(usually about six weeks after the infection cleared)
What joint is most commonly affected by reactive arthritis?
joints of the leg - knee in particular
If the reactive arthritis is combined with conjunctivitis and urethritis, what syndrome is it?
Reiter syndrome
What are the 2 most common microorganisms for septic arthritis?
staph aureus
neisseris gonorrhoeae
Staph auerus is usually the most common cause of septic arthritis overall, but in what population is neisseria gonorrhoeae the most common?
sexually active individuals under age 30
What are the two musculoskeletal syndromes caused by disseminated gonorrhoeae?
- arthritis-dermatitis syndrome
- localized septic arthritis
What happens in arthritis-dermatitis syndrome?
arthralgias
skin lesions
inflammation of tendons
NOTE: the septic arthritis is rarely found at the same time as the bacteremia (that comes first)
WHat happens in localized septic arthritis?
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…
Which phenotypes of gonococci are more likely to disseminate? When do they?
The phenotyes that are expressed during menstruation are more likely to disseminate, one week after the start of menses
Is GC more or less likely to disseminate in homosexual men?
less likely
True or false: strains that disseminate are more potent stimulators of inflammatory responses and are therefore likely to cuase urethral symptoms.
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
What would show up on labs in GC septic arthritis?
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
What will a GC joint infection look like on gram stain?
gram negative diplococci
(plus lots of PMNs)
What is the treatment for a GC septic arthritis? Does it clear easily?
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
