Drs. Veronica Santos, Sebastian Shrager, and Misti Ellsworth share a not so typical case of Brodie abscess!

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Hi everyone.

Welcome to Febrile, a cultured podcast about all things infectious disease.

We use consult questions to dive into ID clinical reasoning, diagnostics,

and antimicrobial management.

I'm Sara Dong, your host.

I'll start by introducing our guests for this episode.

First up is Dr. Veronica Santos.

She completed medical school at the University of Puerto Rico and is currently

a second year in pediatrics residency at University Texas or UT Health Houston.

Hi, I am Veronica Santos.

We have a returning guest, Dr. Misti Ellsworth.

She's an Associate Professor of Pediatric Infectious Diseases at McGovern

Medical School and UT Health Houston.

Hi, Misti Ellsworth!

And rounding out the team, we have Dr. Sebastian Shrager.

He completed his pediatric residency at Broward Health in Fort Lauderdale,

Florida before completing a fellowship in Infectious Diseases at the University of

Texas Medical Center in Houston, Texas.

He just started his job as an attending at Wolfson Children's

Hospital in Jacksonville, Florida.

Hi, I am Sebastian Shrager.

As everyone's favorite cultured podcast, we like to kick

off the show by asking our guests to talk about a little piece of culture.

Really just something non-work, non-medical related

that brings you happiness.

So, Veronica, maybe I'll start with you.

Sure.

Um, I've been reading a book, We Are Liars, which is now a Hulu series.

I've been really enjoying this book and plan on reading the pre sequel after this.

Very nice.

Sebastian, how about you?

Yeah, so, uh, I'm, I'm really excited for the World Cup.

It's coming to the United States this summer, and I have, uh, tickets to

Germany-Ecuador, and France-Norway.

I'm super pumped.

I'm a big soccer fan and I can't wait.

It's so exciting.

Yeah.

It's gonna be, it's gonna be awesome.

Um, and Misti, how about you?

So I spend most of my free time attending and

embarrassing my tweens and teenagers at sporting events and performances.

When I'm not embarrassing my kids, I like to read and I'm also really

enjoying the, uh, Shrinking series.

All right, well, today's consult question I have heard is about

ankle pain, so I will hand it over to Veronica to tell us about this patient.

Yes.

So to start with, we have a 14-year-old female.

She came in with chronic, intermittent right ankle pain for the past three

years, and she presented with acute worsening over the last 10 days.

Her right ankle pain was intensified during soccer practice.

Three days later, pain worsened and she was now unable to

bear weight on her right foot.

She had two separate visits to urgent care where x-rays were normal and her

pain was attributed to tendonitis.

On day nine, after orthopedics evaluation, MRI of the right foot and labs were done.

On initial exam, her vitals were notable for temperature of 98.2, heart rate of 84,

blood pressure of 115/60, respiratory rate of 15 and saturating at 97% in room air.

On focused physical exam, she had swelling diffusely about the right

heel with tenderness to palpation and a positive squeeze test.

There was no erythema, warmth, or induration noticed and sensation

and active movements were intact.

Her initial labs were significant for a marked increase in inflammatory

markers with no leukocytosis.

Her CRP was 115 and her ESR was 39.

She had slight decrease of hemoglobin to 11.8 with normal platelet count.

Further workup included right ankle MRI, which was remarkable for a

3.8 cm proteinaceous cyst in the calcaneal tuberosity with adjacent

patchy marrow edema and enhancement suggestive of a Brodie's abscess.

The MRI was also notable for edema and enhancement of the quadratus plantae

muscle with a intramuscular fluid collection suggestive of myositis

with possible early polymyositis.

Sebastian, based on this initial presentation, what is your

differential diagnosis so far and would you treat empirically?

Yeah, so great history.

So Staph aureus is king here.

That's the most common organism by far.

You can also see Group A Strep and Strep pneumo, which still show up.

She's a little too old for Kingella.

Um, so that's lower in the differential and she's not immunocompromised or using

IV drugs, so Pseudomonas is less likely.

And then without sickle cell disease, Salmonella drops way down the list.

That said, Brodie abscesses can be absolutely polymicrobial.

Management wise, this is where people sometimes jump too fast for antibiotics.

If the kid looks stable and not septic, I'd actually hold antibiotics

and call our friends in orthopedics.

Incision and drainage gives you the best chance of finding a bug and holding off

on antibiotics will increase that yield.

What if they say no to an I&D (incision & drainage)?

Yeah.

Um, well, I'll try to persuade them first, but if they still say no, then

cefazolin alone is totally reasonable.

It covers MSSA well and makes oral step down easy to cephalexin, or

cefadroxil, which are great PO options.

If you're living in a MRSA heavy area, then vancomycin makes sense.

And then if you want to also cover gram-negatives and MRSA, you could

do ceftriaxone and vancomycin.

Those are all great differentials.

Now how about I give you more history to see if we can add anything else?

She was born term with no complications.

Her only medical history is tendinitis of her right ankle for the past three years.

She has no pertinent surgical history or family history.

Her vaccines are up to date.

She does have pertinent travel history that include a trip to Galveston

Beach in Texas where she stabbed her right ankle on a piece of wood.

The piece of wood was spontaneously expelled from the

puncture site two weeks later.

About five months prior to presentation, she also went swimming in Pensacola

Beach, Florida, and about two and a half months prior, she went

swimming on Canvasback Lake, Texas.

She refers exposure to multiple animals, including ticks, fleas,

mosquitoes, horses, cattle, chickens, possums, iguanas, and even field mice.

And she also has two vaccinated dogs.

How does your differential change now with this additional history, Sebastian?

So be careful when you go to Galveston Beach, it looks like,

'cause you can get poked with a stick.

Um, now this case gets more interesting because of the water and wood exposure.

Uh, you have to think about Mycobacteria marinum, which loves salt and brackish

waters, and fits a slow indolent course.

The Vibrio species as well, especially vulnificus and alginolyticus,

even though we usually think of them as more aggressive.

She also swam in lakes, so Aeromonas hydrophilia comes into play plus

rapid growing mycobacteria, since they're literally everywhere,

everywhere in all water and soil.

The wood exposure opens the door to fungi like Sporothrix schenckii, probably

lower on the list, but not zero, which really drives home the key point.

Send the bone.

Get aerobic, anaerobic, AFB and fungal cultures because with Brodie's abscesses,

especially with environmental exposure, the diagnosis lives in the microbiology.

I'd also keep a sample on the side to send the PCR testing, just

in case the cultures don't grow.

We really do have a broad differential.

I think at this point we're all ready to get some answers.

So our patient underwent two I&Ds by orthopedics.

To our surprise, the pathology and cultures sent from the operating room

revealed Vibrio vulnificus causing acute osteomyelitis, Brodies abscesses,

myositis and bursitis of the right ankle.

The patient was then transitioned from IV vancomycin and piperacillin-tazobactam

to ceftriaxone and doxycycline.

Sebastian, can you talk more on Brodie's abscess, because this

is one of those diagnoses that feel rare and it actually is.

Yeah, exactly.

Yeah.

So first off, pediatric osteomyelitis overall isn't that common?

It's only about 2 - 20 cases per a hundred thousand kids, and Brodie abscess

makes up only around 2% of those cases.

So you're already dealing with something pretty unusual, and what makes it

tricky is that it's, it's not your classic toxic looking osteomyelitis.

A Brodie abscess is really a subacute form of hematogenous osteomyelitis.

Instead of widespread infection, you get this localized intraosseous abscess,

basically a smoldering infection that the immune system has partially contained.

Which makes sense in kids, right?

Yeah, totally.

So most pediatric osteomyelitis comes from the bloodstream, right?

And the growth plates have this unique vascular anatomy with

slow flow, looping vessels.

Bacteria get in.

The immune system walls it off, and instead of clearing it, you

end up with the Brodie's abscess.

Location wise, Brodie's abscesses love long bones.

Tibia is the big one, about half of the cases, and then the femur.

And interestingly, uh, Brodie abscesses tend to involve the diaphysis more

than the metaphysis, which is a little different from what we usually think

about with acute osteomyelitis in kids.

We were all surprised by Vibrio vulnificus

being the causative agent.

Dr. Ellsworth, can you share more on why this was such an unusual case?

So what made this case really interesting to us is

how completely un-Vibrio it was.

So when we think about Vibrio vulnificus, we usually think about

very dramatic, very fast infections.

So someone cuts their leg in seawater and within days they're septic.

They've got hemorrhagic bullae, necrotizing fasciitis.

Sometimes they end up even in the ICU.

Osteomyelitis just isn't what comes to mind when we think of this bug.

And in fact, when you look at the literature, Vibrio

osteomyelitis is incredibly rare.

Most of what's out there are single case reports.

There aren't any case series and there aren't guidelines talking about it,

and Vibrio doesn't even show up on the usual list of osteomyelitis pathogens.

One of the few detailed reports is from the Journal of Infectious

Diseases in 1990, and that case really mirrors what we saw.

In that report, the patient had a fairly typical exposure, brackish water and a

skin injury, but instead of progressing rapidly, the infection kind of smoldered.

He initially improved with the antibiotics, but over the course

of weeks to months, he developed worsening pain and swelling and

eventually imaging showed osteomyelitis.

The total time course was about 13 weeks, which is just not how

we're taught that Vibrio behaves.

That's what made our patients so challenging.

There was no explosive presentation, no early sepsis, no

necrotizing soft tissue infection.

It said it almost looked like an orthopedic or an inflammatory

condition at first with this chronic pain, local tenderness, no skin

findings, and that really delayed the diagnosis in this patient.

What's striking is that Vibrio infections are usually the opposite of indolent.

Large surveillance studies showed that they present as gastroenteritis,

wound infections, or primary septicemia, not chronic bone disease.

Even during outbreaks, osteomyelitis is almost unheard of, and one Israeli

outbreak with over 60 invasive cases, only one patient developed

osteomyelitis, and there's not a whole lot of details in that case.

So the big takeaway for us was this.

Marine exposure plus persistent focal symptoms should keep

Vibrio on the differential, even if the timeline feels wrong.

Partial treatment, early antibiotics, or lack of source control may

blunt that classic fulminant course and allow a deep infection like

osteomyelitis to slowly declare itself.

And finally, this case is a good reminder that when symptoms don't resolve,

especially pain, repeating imaging and getting deep cultures really matter.

Because even organisms we think of fast and furious can occasionally surprise

us by being slow, quiet, and sneaky.

Thankfully despite the chronicity of this

infection and it being Vibrio, our patient had really good outcomes.

On day 15, the second OR culture was positive for Vibrio vulnificus.

On day 16, her inflammatory markers were down trending, and the patient

was doing better clinically.

After completing three days of IV antibiotics, she was sent home with

one month supply of doxycycline.

Patient was followed up in clinic one month after.

At this point, inflammatory markers continue to downtrend with ESR

at 41 and CRP less than three.

The patient completed 12 more days of doxycycline for a total of 42 days.

On day of completion, her ESR level was at 19 and CRP

continued to be less than three.

The patient was later cleared by orthopedics to return to soccer play.

The takeaway from all of this is to think that Brodie's abscess can be subacute,

smoldering, a form of osteomylitis that often lacks systemic toxicity.

When able, as Sebastian said, always send the bone, deep OR culture

should include aerobic, anaerobic, AFB, and fungal cultures, especially

with environmental exposures.

Plus marine exposures and persistent focal pain should always keep

Vibrio on the differential, even when the timeline feels wrong.

Thanks so much to Veronica, Sebastian, and

Misti for joining Febrile today.

Don't forget to check out the website febrilepodcast.com, where

you'll find the Consult Notes, which are our written show notes for the

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Febrile is produced with support from the Infectious Diseases Society of America.

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Thanks for listening.

Stay safe and I'll see you next time.