Infectious Arthritis

Question 1

first thought with a monoarticular arthrits

Answer 1

SEPTIC arthrits. must rule out septic arthritis in any pt with an acute monoarticular arthritis, esp. if pt is febrile or appears toxic or if there is an extra-articular site of infection. Remember that 10-20% of cases of septic arthritis are polyarticular.

Question 2

Septic arthritis

Answer 2

usually monoarticular but 10-20% are polyarticular
predominantly large joints
athrocentesis is mandatory
mortality can be as high as 50%
pre-existing arthritis and prosthetic joints are risk factors.

Question 3

causes of acute monoarticular arthritis

Answer 3

pyogenic bacteria
crystal arthritis
trauma
hemarthrosis
acute onset of RA, PSA, SLE, Reiter's
acute onset of TB or Lyme
Rheumatic fever

Question 4

Etiology of non-gonococcal septic arthrits

Answer 4

S. aureaus (then Strep. gram neg bacilli in elderly or immunocompromised or in foot infections)

Question 5

Organisms for septic arthritis and Hx/PE findings

Answer 5

gonococcus: female during period or preg; sexually active young adult
meningococcus: >100 skin lesions
human bites, cat or dog bites, rat bites, tick bites

Question 6

synovial fluid analysis for infectious arthritis

Answer 6

gram stain and culture, cell count and differential, and look for crytsals

Question 7

gonococcal arthritis: history and physical

Answer 7

migratory arthritis and/or tenosynovitis in a sexually active person: consider disseminated gonococcal infection
skin lesions may be characteristic: small pustules. also may see dactylitis: entire finger swelling.
women are especially susceptible during period and pregnancy

Question 8

gonococcal arthritis: diagnostic tests

Answer 8

blood cultures only positive 13% of time- must do GRAM STAIN of synovial fluid. Extra-articular cultures (GU, rectal or throat) may be helpful.

Question 9

gonococcal arthritis: predispositions

Answer 9

women are especially susceptible during period and pregnancy

abnormalities in later parts of complement cascade predispose a pt to disseminated gonococcal infection.

Question 10

viral arthritis: what viruses?

Answer 10

seen with many common viruses, including EBV/mono, parvovirus B19 in an adult, HCV and HBV (pre-icteric for HBV), rubella (including post-vaccine), retroviruses, alpha viruses (arboviruses are alpha viruses)
ask about skin rashes in kids when an adult presents with inflammatory arthritis.

Question 11

Lyme disease and arthritis

Answer 11

stage 3 lyme disease. borrelia burgdoferi. often preceded by erythema migrans (target rash). may have CNS and cardiac effects.

Question 12

Lyme disease Dx

Answer 12

erythema chronicum migrans, inflammatory arthrits, neuro/cardiac manifestations. Serology is marginally helpful.

Question 13

Rheumatic fever dx

Answer 13

2-3 wks after untreated GAS infection (group A strep)
major criteria (2 are diagnostic. minor criteria exist but I won’t learn them):
carditis, syndenham’s chorea (face, hands, and feet), polyarthritis that may be migratory, erythema marginatum (lesions on extensor surfaces), subcutaneous nodules
adults may get only migratory arthritis

Question 14

Tx of rheumatic fever

Answer 14

high dose aspirin; steroids for cardiac disease. prophylaxis to prevent re-infection.

Question 15

reactive arthritis

Answer 15

post-genital infection or GI infection. linked to B27 cross-reactive HA class I.
associated with conjunctivitis and iritis, prostatitis, cervicitis, salpingitis and/or vuvlvovaginitis, keratoderma blennorrhagica (weird rash)
May have AORTIC REGURGITATION and PERICARDITIS
Reiter’s: reactive arthritis PLUS inflammation of the eyes and urethra (can’t pee, can’t see, can’t climb a tree)