Evaluating Allergic Fungal Rhinosinusitis (ARFS): Symptoms & Diagnostic Criteria

[Dr. Amber Luong]
Allergic fungal rhinosinusitis is basically a subtype of the bigger chronic rhinosinusitis with nasal polyps. We have chronic rhinosinusitis with and without nasal polyps. When we start looking at the nasal polyp group, allergic fungal falls under that. The reason why it's been carved out is because of some of the unique features of this disease. Some of which includes sometimes such severe presentation that the sinus cavities are so expanded that you get these really impressive CT scans where the frontal sinus is expanded into the intracranial cavity, not necessarily invading it like you alluded to, but more just because it's been there for so long and expanded the sinus cavity outside of its normal dimensions. It can expand into the orbital area.

Luckily, oftentimes, it's still preserved within the sinus cavity, but you get these really dramatic CT scans. Also on CT scans, you get a presence of this really thick, it's been described as “peanut butter mucin,” really sticky, thick mucin. Then these patients have an allergy sensitivity. If you did skin testing or blood testing, they do have elevated IgE level to the various different fungal antigens. The other characteristic is that when you look at the total IgE level, it's like out the roof. You see elevated IgE levels in allergy patients, but maybe in the hundreds in allergic fungal rhinosinusitis, it's in the thousands. Almost following into that category of hyper IgE syndromes such that we see in the thousands. It's a really unique phenotype and subtype of CRS with nasal polyps.

[Dr. Gopi Shah]
When you diagnose it, can you pretty much diagnose it then on CT or are you then in your workup checking off the-- are we still doing the Bent & Kuhn Criteria or how do you actually diagnose it clinically? Are you just looking at the scan and then look in the nose, if you see some peanut butter and you're like, Oh, that's probably AFS or are there certain things in your checklist that you want to make sure that you have?

[Dr. Amber Luong]
Yes, great question. Actually, the Bent & Kuhn Criteria has been a great criteria for us to make this diagnosis. One of those is, the nasal polyps we talked about, the eosinophilic mucin, CT changes, but it turns out that the more we are starting to talk as a community, a worldwide community, where we're starting to realize that there are several patients that you can check mark and meet them at Bent & Kuhn Criteria, but it either has a different presentation in different geographic locations or they're totally different things. It's confusing because in the South where we live, in the Southern regions, you get that classic allergic fungal, exactly what we talked about, this thick peanut buttery mucin, the fungal allergies, the expanded CT scans, but then when I talk to my colleagues, let's say in Canada, where they make the diagnosis of allergic fungal, they may have the fungal-specific IgE elevation, so a fungal allergy, but they don't get the same expanded CT scans.

They don't get the same really thick peanut butter, although they do get some sort of eosinophilic mucin. The question is whether or not these are the same diseases. I think those of us in the south that see the classic ones, I would say that it's probably going to turn out to be different than what they see up north, which is more of an eosinophilic serous with nasal polyps. I don't know if that's going to make any difference right now.

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[Dr. Gopi Shah]
I wanted to ask about, do we know why there's that geographic difference? Does it just have to do with certain fungi being in certain places like in the south that aren't up north? Does it just have to do with that part of the environment? But then now I also want to make sure that we touch on endotypes and expand on that as a definition. I don't know what would makes sense to cover first.

[Dr. Amber Luong]
Yes, so, great questions! In terms of geographic distribution, we believe, so this was described many years ago by another fantastic woman rhinologist, Dr. BJ Ferguson. She was the lead author on this paper that talked about the geographic distribution of allergic fungal rhinosinusitis. It turns out that you do get much higher level of prevalence of AFRS in the south. I don't know if we know exactly why we do get this geographic distribution, but it sort of supports the concept that there is an environmental trigger to this disease process. That there must be an underlying genetic defect. Otherwise, everyone in the south would get it. There also must be a geographic, maybe the levels of fungus more than the actual presence of specific fungi, because a lot of these are very much prevalent everywhere. Staph aureus, similarly. Fungus, the different species are actually quite prevalent in most places. It's just that in the south where it's hot and humid, the duration of the year where you get these high levels of fungus is going to be longer than, let's say, in the north where you get these very distinct seasons and so you get a really cold front, so it kills all these spores while in Houston, we're happy if we get two weeks of where it drops into the 30s. Probably similar to Dallas, although it gets a little bit colder there. I think that's why we're seeing some of this distribution. Also, you'll see the distribution closer to like in the US around the Mississippi Basin.

There it's, again, humid, more prevalence, and higher loads of fungus. I think allergic fungal is unique in that it does really highlight this environmental component along with the probably genetic component of chronic rhinosinusitis more so than other endotypes.