Emergency Medicine Forum

A 26 y/o female presents with left knee pain.  She notes the pain started 2 days ago.  It hurts to walk on it, but she can bear some weight.  She has a history of Lupus (SLE=Systemic Lupus Erythematosus), so mild joint pain is not unusual, but now her knee is swollen, and this is different from her usual joint aches.

ROS:  She has felt feverish at home (but did not take her temperature). Some mild chills.  No vomiting or diarrhea.  No chest pain, shortness of breath, cough, abdominal pain, dysuria, frequency or urgency.  No vaginal discharge, no rashes, no sick contacts, no travel. No new pain anywhere but her knee (all her joints always ache a little).
PMH:  Lupus for the past 2 years.  Controlled on Ibuprofen now.  Has been on steroids in the past, but last burst was 1 year ago.  Her Lupus doctor is on staff at a neighboring hospital.  No hospitalizations or surgeries.
SH:  No smoking, social alcohol consumption.  Not married, one sexual partner. No history of IVDA or drug abuse. 
Meds:  Ibuprofen.  Last dose 3 hours ago.
PE:  WDWN articulate black female, lying on the cot in no acute distress.
VS:  HR=98, RR=18, BP=135/82 Sat=97%, Temp=99.5F
HEENT:  PERRL, neck supple, mild erythema to tonsilar area.  Minimal lymphadenopathy to anterior cervical area.
Heart:  RRR no murmurs
Lungs:  Clear
Abd:  Soft scaphoid, non-tender, no masses
Ext:  Left knee warm to touch.  Difficult to appreciate erythema as skin tone is very dark.  Tender to Range of Motion (ROM) testing. Effusion is palpable.
Skin: Small macules noted on dorsum of right and left hand.  Per patient she thought they were bug bites.  They are non-pruritic, and non-tender

Questions:

1.  What is the likely diagnosis?

One of the biggest concerns is septic arthritis.   Septic arthritis is usually divided into Gonococcal arthritis (most common cause (75%) in sexually active young individuals) and Non-Gonococcal arthritis (usually caused by staph aureus (most common) or strep, or gram negative). (1)

This patient has several risk factors for Gonococcus arthritis.  She is female, black, has a history of SLE (Lupus), and is under the age of 30. (2) While other infectious causes also need to be considered, given her skin lesions and risk factors, GC becomes more elevated than the usual culprits for Septic arthritis. 

Disseminated Gonococcus infection is more likely in African American, Hispanic and Native American populations (2).  It is 3-4 times more common in females (believed to be related to the increased risk of asymptomatic infection in females).  It’s not clear why Lupus increases the risk.  Patients with extra-genital infection (i.e. pharynx) with GC are more likely to get dissemination of this infection.  Pregnant women and those on their menses are also more likely to get this disseminated infection. (2)

There are actually two types of GC arthritis: (2)

A. Bacteremic form (Arthritis-Dermatitis Syndrome) (1)

 1.  In this infection, the most common presenting complaint is arthralgia (as opposed to arthritis) which may be migratory, and usually polyarticular.  The arthritis is more likely in the upper extremities (wrist, elbows) than lower extremities (ankles and knees).  In 30-40% of the cases, the arthralgias may evolve into a septic arthritis in one joint. 
 2.  The rash in this case is frequently overlooked as it is painless and non-pruritic.  It consists of small popular, pustular, or vesicular lesions.  I think if the lesions were pustular, the diagnosis would have been even more clear, but her lesions were simply small papules that she didn’t even consider significant (she thought they were bug bites)

B. Septic arthritis (1)

 1.  The joint symptoms begin within days to weeks of GC infection
 2.  Joint is red, swollen and painful.  It can affect more than one joint.
 3.  There are not usually skin manifestations in this gonococcal infection.

2.  Will the joint fluid give you the diagnosis? What do you order on the joint fluid? Where is the best place to culture besides the joint fluid?

This is interesting. The joint fluid only shows the organism (either by gram stain or culture) in 25-30% of the cases of GC arthritis from disseminated GC (2).  In those with isolated GC arthritis, the positive culture rate is 50%. (2) The organism is frequently (90%) found at the primary site of infection (if the infection is still there).  In this case her pharynx was inflamed, so I did culture it for GC.  I also cultured her cervix (although she had no complaints of vaginal discharge, there was some vaginal discharge present when I did my cultures).  You may need to specify to the lab the need to culture for GC as many culture mediums may not be able to grow this organism. 

As is true in any joint fluid analysis in the ED, I ordered an exam for crystals, culture, gram stain, CBC, and glucose.  For a quick review of the types of results in the different causes of joint effusion, see reference 3(3). 

In GC joint infections, the gram stain is positive (gram negative intracellular organisms) in less than 25% of infections. (2)

3.  Should you start antibiotics?  If so, what do you need to cover?

The joint fluid came back with 60.000 WBC, 92% PMN, her CBC showed a peripheral WBC of 12,000 with 80% PMN. 

I did cover her with antibiotics for presumed Septic arthritis.  I gave her Ceftriaxone 1 gm to cover GC, and also gave her Vancomycin in case it was staph (although I doubted it).  As my suspicion for GC was high, I also gave her one time dose of Zithromax (I had already cultured her for Chlamydia) to cover for this very common additional STD. 

Outcome:

X-ray of the joint did not reveal any abnormality other than the effusion.  Two hours after arrival she spiked a temp to 101F. (Her Ibuprofen had likely worn off.)  Joint aspiration resulted in milky fluid which was sent for crystal, CBC, glucose and gram stain analysis.  Gram stain result was negative.  Joint fluid showed WBC >50,000 (70% chance of septic arthritis) (3).  Antibiotics were started after blood, throat, joint and cervix were cultured. 

Unfortunately, her insurance required us to transfer her to another hospital, but two days later the pharynx culture was positive for GC.  This was relayed to her treating doctors at the other hospital.

It’s interesting that she never complained of a sore throat, but this was likely the site of initial infection.  Also, we have all seen the patient with only one active partner, who (unfortunately) contracts an STD.  

These discussions with patients about the probability they have an STD are always very delicate.  My personal approach (and I’d love to hear others) is to be non-committal until the final diagnosis is determined.   Also, as many of these infections may have been contracted at an earlier time (i.e. asymptomatic infection); I always leave the door open that the infection may not have come from the current partner. 

For me the discussion usually goes:  “I’m very concerned you have a serious infection, and sometimes this can be caused by a sexually transmitted disease. We won’t know for sure if it is a STD until the cultures confirm it, but I’m going to treat you for all possible causes (STD and others) until we have more information.  Also, some women carry this STD infection for some time and don’t know it, so it doesn’t necessarily prove you got it from your current partner.  I’m sure you will want to notify him about the possible infection, but it may have been present before you and him became intimate.“

References:
1.  Brusch JL.  Septic Arthritis.  Emedicine.  Aug 25, 2008.  Accessed at:”http://emedicine.medscape.com/article/236299-overview”
2.  Keith MP Gonococcal Arthritis.  Emedicine Aug 17, 2007.  Accessed at: “http://emedicine.medscape.com/article/333612-overview”
3.  Clinical Lab Navigator Synovial Fluid Analysis.  Accessed at: “http://www.clinlabnavigator.com/Tests/SynovialFluidAnalysis.html“