Clinical Case: Knee Pain Flashcards
Reactive arthritis
Acute asymmetric arthritis following urethritis (chlamydia) or gastroenteritis
6 weeks after infection
Joints of legs (knees)
May also get conjunctivitis + urethritis = Reiter’s syndrome
Septic arthritis (monoarticular) - two organisms
Staph aureus - most common overall, patients usually have pre-existing joint problem or IV drug users
Neisseria gonorrhoeae - most common organism under age 30
Joint aspiration to know
Dx of GC arthritis
H/P
Lab - WBC high (above 10,000)
blood cultures frequently positive (not always)
joint aspiration shows WBC over 100,000 (not specific)
Gram stain and culture PRIMARY
tx of GC arthritis
3rd gen cephalosporin
oral macrolide abs (azithromycin) also indicated for presumptive tx of chlamydia
prognosis usually good w/ rapid resolution of sxs and signs
Septic arthritis commonly caused by
Staph aureus
or Neisseria gonorrhoeae
Urethritis, conjunctivitis and monoarthritis is called
Reiters syndrome
Gout
Uric acid crystals precipitate in joint
Very acute onset
Most common site in great toe
Low grade fever
Pseudogout
Looks same as gout
Cause: calcium pyrophosphate crystal deposition
Can involve same joints (feet, knee, wrist, ankle) + Shoulder and hips
acute monoarticular arthritis definition
acute joint inflammation that occurs days or less before seeking attention
acute monoarticular arthritis differential
gout, pseudogout, reactive arthritis, septic arthritis
Gout dx
Dx: joint aspiration, polarized light demonstrates negatively birefringent crystals
pseudogout dx
Dx: Joint aspiration, positive birefringent crystals
Reiter’s syndome
Reactive arthritis + conjunctivitis +urethritis
GC arthritis - two musculoskeletal syndromes form disseminated GC
Arthritis-dermatitis syndrome - arthralgias, skin lesions, inflammation of tendons
Localized septic arthritis - septic arthritis and bacteremia rarely found at same time (knee most common)
Neisseria gonorrhoeae
bacteria - gram (-) - diplococci - oxidase (+) - only glucose oxidizer
Neisseria gonorrhoeae virulence factors
specialized pilli - allows attachment to mucosal surface, antigenic variation to evade host defenses, prevents phagocytosis
Endotoxic
Capsule
IgA protease
Media used for isolated N. gonorrhoeae
Thayer-Martin
Most common cause of septic arthritis in sexually active people
N. gonorrhoeae
NG pathogenesis
attach via pili to mucosal cells of urethra and vagina - evades mucosal IgA Ab via IgA protease. Endocytosed by cells. Kills cilliated cells. –> inflammatory response leading to urethritis and cervicitis.
