All right, so welcome back to the Internet Book of Critical Care Podcast.

I'm here with Adam Thomas, and we're going to attempt to tackle the white whale that is hemophagicacetic lymphohysiocytosis.

It's with some trepidation that I approached this, and I've put this off for a while since I was terrified that we'd get assassinated on Twitter, but you know, we have to just go ahead and try to do this.

Don't lie, Josh, you're a little bit excited to do this because we've alluded to it twice before,

but it took a pandemic to really bring this to the forefront of people's minds and accept the

conversation, shall we say?

Yep.

Correct me. Josh knows that I say things wrong all the time, but hemophagocytocin.

Lymphal histocytosis.

In the past, we covered it with our septic shock, posts, and with the ICU-level influenza illness.

So, Josh, today, it's not going to be that long of a podcast, but it's going to have

some small evidence and then some non-evidence areas. Is that fair to say? Yeah. Yeah, there's

overall a deficiency of high quality evidence on this topic, like every other topic in the

internet book of critical care. So we can just preference that for the entire cast. Now let's talk about the basics then. What is HLH and why is it our white whale?

Yeah. So HLH basically describes like a type of immune dysregulation. There's a picture of it

in the chapter, but basically it involves a lot of circular auto amplification loops that involve CD8

positive T cells and macrophages and tissue injury. And essentially, a lot of cytokine

release where all of these cells kind of just spiral out of control. And this is very challenging

to define as far as what is primary HLH, what's secondary HLH. You know, there's probably some patients

with sepsis who have a little bit of this type of inflammation.

And then there's some patients with a lot of this type of inflammation.

And where exactly do we draw the line and say, this patient has HLH?

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