269. When to suspect pemphigus in dogs and cats

Welcome to The Dermvet Podcast. I'm Dr. Ashley Bourgeois, a board-certified veterinary dermatologist practicing in Portland, Oregon with animal dermatology clinics. I'm also a mom of two just trying to find the balance like everyone else. Let's learn to ditch the itch, cytology, everything, and make dirt more fun than frustrating. One of the more common autoimmune diseases that we see in dermatology is Pemphagus Folletius. I love a good Pemphagus case, but I want to give you some tips between dogs, cats, and your diagnostics that you can feel confident you're dealing with the Pemphagus case. I do think there are a couple signs that can put this on your radar, and it can be more difficult than you think. We often think autoimmune diseases will look really obvious, but it actually can be quite difficult because some of these cases are crusty and infected, and they can mimic things like allergies. But there are some signs that can really just get you suspicious. You might be dealing with it, but I do want to give you some grace. Just a little comfortable knowing it's not always straightforward. Sometimes we have to do things like treat infection, kind of see how they respond, biopsy not really knowing what we're dealing with. I have biopsy cases where I think it's going to be Pemphagus, and it comes back as you know, some really weird characterization or allergy. There is definitely some more straightforward cases in cases that are not straightforward, but these are some hints, tips, tricks that can give you the indication that, "Hey, I might want to have Pemphagus on my differential list." Let's start with dogs. Dogs being a little bit more classic with some of their symptoms compared to cats, which we'll get into. They're kind of their own little unique situation when we're talking about signs with Pemphagus volatious. Dogs, some of the big hints I want you thinking, "Okay, maybe Pemphagus volatious should be on my list." Dogs tend to get really like yellow adherent crust. You'll get yellowed here in crust. It'll look different than infection, though. It really can look just like a pyoderma, and it can be difficult to tell, but it'll be thicker. Some people will call this honey color crusting, so the type of crust that is there, the location. So if they kind of have widespread lesions throughout their trunk, it's adherent. It's thick. Of course, you're going to do things like cytology, and we'll talk a little bit about cytology and what can give you an indication that you might be dealing with PF. But it'll be kind of in a weird distribution. You might get a lot of like facial adherent crusting, which can happen with pyoderma and allergies, but it's just not as common for us to see. So if you get kind of honey colored adherent crusting throughout the body, you're just seeing inflammation under the microscope. I want you thinking, "Hey, maybe I'm dealing with some sort of autoimmune case like Pemphagus volatious." Now, a big sign that you could be dealing with Pemphagus should be if the nasal planum is affected. That just should not happen with allergies. If the nasal planum is ulcerative, if it's crusting, if it's depigmented, then something like Pemphagus should really be on your radar. You'll often see like facial lesions that progress to the nasal planum. You can see other areas affected too, like the popads. Again, you have accrusted popads on a dog. That is not going to be allergies. That's either going to be something like an autoimmune disease. It could be a sign of systemic internal disease like hepatocutaneous syndrome. It could be a sign of lymphoma and neoplastic disease, but having really thick, crested popads is one of the more common presentations that Pemphagus volatious can have. When I start evaluating a dog, I'm looking at their skin. I'm seeing a honey colored crusting. The pattern just doesn't seem classic with allergies. Their history doesn't seem classic with allergies. They were never paritic, maybe before the crusting started. Then I always flip over the popads and look because if I see really thick, crested popads, that's a good indication to me that we're dealing with something like Pemphagus volatious. I'll know biopsies probably the best bet as far as my next diagnostic step. Now, the big thing to recognize autoimmune diseases, neoplastic diseases, we often talk about the mucus membranes. Pemphagus volatious really should not affect the oral mucosa. It can affect the nasal planum. It can affect popads. It should not affect the oral mucosa. If you get a patient that kind of looks like Pemphagus and you look at the oral cavity and on the oral mucosa, you have ulcerations and lesions. That's going to be more indicative of a more severe form of Pemphagus and dogs called Pemphagus vulgaris, which is pretty rare. I think I've seen twice in my whole career, and it can just be quite difficult and have a poorer prognosis. So you do want to look, we should be biopsying. You definitely want to make sure those lesions get sent to a German pathologist and you want to biopsy the oral lesions because there can be really specific signs to look for Pemphagus vulgaris. And it's a deeper form of Pemphagus, but oral lesions on the mucosa should not happen Pemphagus volatious. So it's a good thing to look for just to one. Make sure you get good biopsy sites. But two, it helps with prognostic indicators because Pemphagus vulgaris can be a poorer prognosis compared to Pemphagus volatious, but it's quite rare. We see Pemphagus volatious all the time. We don't see Pemphagus vulgaris that often, but something that you can really pick up on is whether or not they have oral lesions within their, you know, the cheeks, the mucosa itself. So those are some big things with dogs, honey color, crusting, crusty paw pads, nasal plenum affected, a lot of facial lesions, cats. You talked about cats with Pemphagus quite often because they are kind of tricky. They often have their cloth folds affected. So if you get swollen cloth folds in a cat, if you get a lot of cacious debris, perilin debris sitting at the cloth folds as my, when I really good friends, Dr. Julia Miller says cheesy cloth folds, cheesy cloth folds should really indicate, whoa, Pemphagus. And that's not what we see in dogs. We don't usually see cloth fold lesions in dogs with Pemphagus volatious. We see cloth fold lesions in dogs because they have a secondary infection from allergies. We see that all the time. We do not see cloth fold infections that often in cats due to allergies. So the most common presentation I see in my clinic is a cat is presented with a resistant bacterial infection in the cloth folds. If I see perilin debris or a presentation such as resistant bacterial infection in the cloth folds in a cat, I'm thinking Pemphagus before even see that cat because it's just such a common presentation we see. Now, some of the other things because it's not always just cheesy cloth folds and cats. Some of the other things we can see are crusting. You can see it diffusely. I've had one cat ever have crusty pop ads. I diagnosed it last year. It's not as common for us to see with cats, but I have seen it. We see it more often than dogs. But two things that are unique to cats besides cloth folds are they like to get parry area areas. So around the nipples, they will get thick crusting. If you see crusting that's specifically around the nipples and cats. Again, that should really indicate to you Pemphagus foliage is being on the list. The other thing that's quite unique to them and you can see this actually in dogs too is lesions on the pinna. So with cats, it's not that common for them to get pinnel infections from allergies. We do see it in dogs. They'll get red inflamed itchy pinna, not that common for us to see in cats. So if the convex or concave portions of the pinna and a cat have really thick crusting or iratheema present, I'm definitely thinking of Pemphagus foliage. So with cats, cloth folds, nipples, pinna, I'm thinking Pemphagus. In it's tricky, right? Because a lot of times cats, since they don't like taking oral medications, we'll get long acting steroids and injectable antibiotics. They'll get injections of steroids that last for a couple of months and they'll get injections of antibiotics. So they'll get better. And so will allergies, right? If you give a cat with allergies, steroids in antibiotics and they have allergies with an infection, they will also get better. So that history of responding to steroids or antibiotics is a different is not a differentiator. So that can be really hard because I have had cats actually present to me in the clinic. You know, they will present looking pretty good because they just got steroid injections. I'll talk to the owner. I'll get their history. And I'll say, man, I'm not really sure what's going on. I'm a little concerned. They could have an autoimmune disease based on the presentation. You're telling me or often they have pictures on their phone from when the cat did have lesions. So we will actually wait. We'll let that steroid wear off. They'll bring them back when they have lesions present. So I can see what's going on. And I've often delayed things like biopsies or cytology or diagnostics that the cat's not showing lesions when they're actively seeing me and we'll let that steroid wear off. And then have them come in and we will reevaluate. So that's just something to take into consideration. You don't have to throw every diagnostic at them when you see them. If they're not that lesional, let things like other medications wear off so that you can see them when they're in their active state of disease. And I hate to make them flare in order for me to see them. But I want to get them on the path to appropriate medications long term and appropriate diagnosis. So I need to see them when those lesions are active. So I can test them and decide what to do next. Now whether you're talking about dog or cat, another good indication that you could be dealing with Pemphagus is of course on your cytology. So on cytology, we've talked about acantholytic keratinocytes before. Acantholytic keratinocytes are just prematurely lifted keratinocytes. So they looked like these big, rounded, fried egg basophilic cells. Those are just skin cells. Skin cells naturally go through a maturation process where they flake off as cornea sites on the off the top layer of the skin after about 21 days. It takes from a baby skin cell to become a cornea site. So it flakes off. That's a skin defense mechanism is to flake off. So pathogens and things leave. That's why we have skin cells all over environment. But what happens is because Pemphagus volatius attacks the Desmasomes, which are the interconnections between keratinocytes, those skin cells don't get to go through that maturation process appropriately. They end up leaving too soon. They retain their nucleus, which they shouldn't. They should lose it. They retain their nucleus and they don't become angulated because they don't get to go through that process of keratinization. And they become really rounded. They become too big, rounded and they retain their nucleus and they're too basophilic. That is that dog or cat skin cells, but they have just lifted too quickly based on how this disease works. So if you see a cantholita keratinocytes, awesome. Like that's a great indication. If you're seeing lots of neutrophils and a bunch of acantholita keratinocytes, you can feel really good you're dealing with a Pemphagus case. There's occasionally other things that can cause it like trichofitin or bad staff infections. They can also cause acantholita keratinocytes, but it's not as common and you usually don't see a ton of them. You still want to biopsy because one, there's different forms of Pemphagus foliacias, but two, you can roll out other things like making sure that there's other indications of Pemphagus that are present. But sometimes you don't get acantholita keratinocytes, especially in cats, they're really stingy with their acas. So other indications you're dealing with this is on cytology. You will collect cytology. You'll see a lot of neutrophils. You know, they're and they're sitting there with really no infection. And if you don't see much infection but see a ton of inflammation with neutrophils because this is a neutrophilic disease and you start to look at the pet and start to realize some of these lesions, you know, don't seem as classic. You definitely want to biopsy. You want a clear infection. If they're super infected, you want to just give them some antibiotics or topicals, clear the infection and then have them come back reevaluate. But if the infections looking pretty good and there's a lot of neutrophils, a lot of crusting on the skin that doesn't really make sense when there's no active infection. Again, you should really consider something like biopsy because that is another way that Pemphagus can present if they don't give you acantholita keratinocytes under the microscope. So those are the big things I want you guys considering for dogs. Again, thick, honey colored adherent crusting, the nasal planum being potentially affected crusty paw pads, you know, facial crusting, doing your cytology, seeing neutrophils with not much infection or seeing acantholita keratinocytes and cats, the three big things, swollen, claw folds, or perulent debris in the coffolds, you know, do your cytology. If you don't see much infection at biopsy, seeing crusting around the nipple area or seeing crusting on the pina, the convex or concave portion of the pina, especially being bilateral, you again, want to consider something like Pemphagus foliasis. If they don't have a lot of lesions, you know, they've been exposed to steroids in the past, give them some time away from steroids or other immunosuppressants, and then have them come back, have the owner let you know when they do have lesions present, so you can evaluate and get them and appropriate diagnosis. So hopefully that makes you feel a little bit more confident when you're seeing these cases, of course, on social media, I do put up pictures of Pemphagus cases just to give you guys some clinical impressions of what this disease can look like. But if you're suspicious, do the work up, do your cytology, clear infection, biopsy, it is okay if you biopsy and it doesn't come back as something like Pemphagus, we always want to make sure we have the right diagnosis. So we set up these cases for success in the long run.