Thread by @WuidQ

#idgrandrounds
1/2
32 F w multiple sclerosis on rituximab, +10d fever, R knee pain in December. Had dysuria tx w/ TMP/SMX 1 wk prior. No trauma. Exam: swollen/tender R knee. No rash. Purulent synovial fluid: 60,000 cells 70%N. Multiple synovial/blood bacteria/fungal/AFB Cx (-)

2/2
No response w/ cefe/vanc. GC/CT(-), HIV(-), Q/Brucella(-), fungal studies(-).
Lives in rural IL, no travel. Denies substance use. Single, sexually active w/ 1 partner. No pets. Unemployed.

Thoughts & DDX? @VarunPhadke2 @TxID_Edu @k_vaishnani @Cortes_Penfield @jdcooperid

1/12
Case resolution:
▪️Synovial fluid PCR +Mycoplasma/Ureaplasma
▪️Successfully tx w/ doxy

Diagnosis: Mycoplasma/Ureaplasma septic arthritis

Good job all of you! @TxID_Edu @VarunPhadke2 @CrystalZhengMD @RashDecisionz @vjhaveri27 @KartikAcharyaID @k_vaishnani

2/12
@VarunPhadke2 laid out a really good problem representation that allows us to frame our DDX:

1️⃣ Immunocompromised (+rituximab) patient + 2️⃣ culture-negative monoarthritis + 3️⃣ preceding GU symptoms

3/12
Infection looms large in this DDX. The most common cause of 2️⃣ is prior Abx use (in this case could be TMP/SMX).

But it also opens a Pandora’s box of atypical infections that hardly grow on routine culture (e.g. fungal, mycobacterial).

4/12
2️⃣ + 3️⃣ pushes our DDX needle to think of reactive arthritis & DGI/gonococcal arthritis as many of you pointed out.

We should also do a diagnostic pause and consider our own biases (is the prior GU symptom a signal or a noise) & entertain other DDX (gout).

5/12
What comes next?

We then try to retrieve illness scripts from prior readings/experiences. Building a compendium of these scripts takes time, experience, and listening to a lot of @CPSolvers episodes 👌@DxRxEdu. This allows us to connect the dots and recognize patterns.

6/12
Mycoplasma hominis & Ureaplasma sp are closely related bacteria (genera separated in 1974) that normally colonize the GU tract.

Dissemination occur w/ mucosal disruption (instrumentation) or immune compromise (esp. humoral deficiency: CVID, CLL, rituximab, etc).

7/12
Septic arthritis is one of the most recognized manifestations. Suspect Mycoplasma hominis/Ureaplasma infection in a patient w/ purulent, PMN-predominant septic arthritis w/ negative GS (lacks cell wall) and Cx, who doesn’t respond to routine abx.

8/12
In this excellent review, more than half of patients had prior GU symptoms or GU instrumentation.
bit.ly/3eNz6H7

Others reported infections include: wound infection, abscesses, endocarditis, and CNS infection.

9/12
Last year, we discussed a recently described association with Ureaplasma infection 👉 post-transplant hyperammonemia (perfect time to review this; see thread 👇)

10/12
Since Mycoplasma/Ureaplasma don’t routinely grown on Cx (requires special techniques), it is hard to Dx. When highly suspected based on clinical presentation, empiric Tx can be started & nucleic acid test (PCR) obtained. +PCR outside of GU tract + clinical SSX = diagnosis.

11/12
Drug of choice is doxy or FQ. They are generally resistant to all beta lactams, slufa, TMP, and aminoglycosides.

12/12
In summary, the illness script for invasive Mycoplasma hominis/Ureaplasma is:

▪️Immunocompromised (humoral)
▪️+/- antecedent GU Sx/procedure
▪️Septic arthritis > wound/CNS/endocarditis
▪️GS/Cx (-), PMN-predominant fluid
▪️No response to routine abx (outside of doxy/FQ)