150 Skin Infections, Bites & Infestations – Pattern Recognition, Treatment Buckets, and Easy PANCE Points

Welcome to the Physician Assistant Exam Review Podcast. Today we’re going to be covering skin infections and bug bites. My name is Brian Wallace. I’m the host and creator here at Physician Assistant Exam Review. And I want you to remember that we aren’t just about medical facts here. We’re about how to think, study, and perform for high-stakes exams. In each episode, we take medical content and break it down to show you how to recognize it on exams and how to organize it when you’re studying.

We also want to show you how to avoid common thinking traps and things that cost you points for the PANCE or on your end of rotation exams or wherever else you need this material. This week, we’re going to continue with Derm, doing skin infections and bug bites. I was going to include viral skin infections here, but we’re going to bump that. It just became too much, I think, to hold on to. So we’re going to do bacterial, we’re going to do fungal, we’re going to do parasites, and then we’re going to do bug bites.

All right, so without further ado, let’s jump right in to our priming questions. Poorly defined erythema and swelling on one shin suggests what diagnosis? Poorly defined erythema and swelling on one shin suggests what diagnosis? A beefy red rash with satellite lesions suggests what type of infection? Annular scaly rash with central clearing suggests what organism type? What’s the bug? What’s the organism?

Intense nocturnal itching with linear lesions in the finger web suggests what infestation? And finally, how should an expanding erythematous rash after a tick bite be treated?

All right, we’re going to begin with bacterial infections. These are usually tested against each other. So you’re looking at depth, borders, systemic features. And then the last part of this is choosing what your treatment is going to be. So is it topical, oral, or IV? That’s really what this section comes down to. So we’re going to hit cellulitis, we’re going to hit erysipelas, and we’re going to hit impetigo.

So a cellulitis is an acute bacterial infection of the dermis and subcutaneous tissue. So it’s a little deep. Most commonly caused by strep pyogenes or staph aureus. Clinical presentation, which is how you’re going to have to pull this out, right, is expanding area of erythema that is warm and tender with poorly defined borders. That part’s important, as you’ll see later on. Skin may appear shiny and tight with localized swelling. And usually this is unilateral involving like one shin or the lower leg.

There’s no vesicles and no crusting. Unilateral makes sense, right? Because this, if it were, I’m trying to think of something else that it would be. If it was something else systemic, it would be in more than one place, right? But because it’s a localized infection, it’s usually going to be unilateral. They may or may not have fever or chills or things that go with it, depending on how far along it is. Here, the question stem is usually going to be something like an expanding warm, tender erythematous area with poorly defined borders on one shin or one leg or something like that.

Physical exam, this is a clinical diagnosis. I’m not going to go through the whole thing. Warm, tender, and there’s edema in the area usually. Treatment here. If it’s mild and there’s really not much going on, This is just going to be oral. So like cephalexin or dicloxacillin, something like that, like a beta-lactam for strep. If you think there may be MRSA, then you might do Bactrim or doxycycline or clindamycin.

And if it’s severe, if there’s a real, you know, obviously this is a problem, they’ve got fevers, there’s a reason to push it over the top, maybe admit this person, then you’re looking at IV antibiotics. So ceftriaxone, cefazolin, or vanco if you think it’s MRSA. The key here is that poorly defined borders thing. So that’s going to be your key to cellulitis. This is deeper than erysipelas, which we’ll get to in a minute. And again, the question is going to come down to defining it and then determining how bad do you think this is? What’s going on here?

Erysipelas is next. This is an acute bacterial infection of the superficial dermis and lymphatics, most commonly caused by strep. Your clinical presentation here is a bright red erythematous plaque with sharply demarcated raised borders so right away we have our clue as to how to tell this from cellulitis whether this is a patient in your clinic or this is a test question erysipelas has clearly defined borders cellulitis does not they sort of fade out so one thing with cellulitis because it doesn’t have clearly defined borders. I remember my wife actually had this years and years and years ago. She had a bug bite at the beach and it wound up getting infected and she wound up getting a cellulitis. And what they did was with a marker, they drew around the area. They sort of created a border of the rash so that we could follow it as the antibiotics took effect to see if they were working or not.

Good idea. Erysipelas will have sharply demarcated borders, which this may be helpful for that too to tell if it’s advancing or not. The skin may appear tense and indurated. This is commonly on the face or lower extremities. I would like to see this on the face for your exam. That’s what I’m hoping for because lower extremity would make you think cellulitis. I mean, impetigo goes on the face too.

That’s sort of what you’re going to be determining between. This is also usually unilateral. You might get fevers and chills with this. And here you’re going to have a patient with a fever and a raised sharply demarcated erythematous lesion probably on the face. Our diagnosis is clinical. Treatment here, if it’s just, again, uncomplicated, just oral meds. So penicillin, amoxicillin, cephalexin, just a beta-lactam for strep.

If it’s more severe, you’re going to go with IV, penicillin G, or cefazolin. Again, just looking for that strep coverage. Those sharp raised borders are your key, and strep coverage is all you need. Also, the face thing may be helpful. I would definitely be leaning in that direction as I studied for my exam. Our last one for bacterial infections for dermatitis is going to be impetigo. It’s a superficial bacterial skin infection.

So we went from cellulitis, which is deeper, to erysipelas, which is a little more superficial, and then impetigo, which is superficial. This is most commonly caused by strep pyogenes and staph aureus, usually in children. This has a lot to do with, if I remember correctly, with cleanliness. So I saw this one time when I was on my emergency rotation. Really cool. I had a resident bring me in to show me the findings because we’ll get to just a second, but this has the classic vesicles or pustules that rupture to form that honey-colored crusted lesions. And they brought me in to take a look at it because it was so clear to see what those honey-colored lesions looked like and why that term comes up.

This patient was, I believe it was somebody who had trouble taking care of themselves. It was an adult, but it was someone who clearly could not take care of themselves. And I think that was part of the picture here. This typically involves the face, especially around the mouth and nose. It may spread rapidly and it’s highly contagious. Systemic symptoms are not usually present. Usually you have a kid who’s got this rash around the face or on the mouth or the nose with these honey-colored crusted lesions and no other complaints.

So that’s going to be your question stem. It’s probably going to be a kid, honey-crusted lesions around the mouth or nose. The lesions here are going to be superficial with characteristic crusting. Treatments. Localized disease is going to be mupirocin or retapamulin. Not sure that’s going to be topical. You don’t have to check the notes on the website, physicianassistantexamreview.com/150 to get the notes for this section.

If they have extensive disease or it looks really bad, you’re going to do cephalexin or dicloxacillin. This will give you strep plus MRSA coverage. If MRSA is a concern, you’re going to do clindamycin.

Exam keys are going to be those honey-colored lesions are going to be impetigo.

Perfect. All right.

Excellent. Now we’re going to move on to fungal infections. Candida is going to be number one. This is cutaneous candidiasis, right? So we’re getting the infection of the skin. You can get it in other places, right? You can get just like strep, you can get in other places.

This is just what we call it when it happens to be in the skin. This is a superficial fungal infection caused by candida. This thrives in warm, moist environments. Those are keys to candida infections, warm, moist environments. This is a beefy red erythematous rash, so it looks really, really red and angry, usually in the skin folds or the diaper area. You can get satellite lesions. So where you have this big, beefy red in the skin folds, you might get these little lesions moving out from the skin folds.

The area may be macerated or moist. I always had trouble with the term macerated. Macerated is if you’re in the pool all day and your fingers become and your skin gets that white, waterlogged type of feel to it, that’s what we’re talking about here. The question stem here is going to likely have a beefy red rash with satellite lesions in the skin folds. Maybe you have an infant with a diaper rash, not improving with barrier creams, something along those lines. This is a clinical diagnosis. Treatment is going to be azoles or nystatins so these are topical antifungals and then if you need to you can get to an oral fluconazole if severe or refractory if you see the term satellite lesions you’re definitely thinking candida and if it’s like in a moist area and that beefy redness is what you’re is what you’re looking at next we have dermatophyte infections so these are your tineas this is superficial fungal infections caused by dermatophytes they’re named by location So it’s Tinea corporis, Tinea pedis, Tinea capitis, right?

Those are all based on the location where you find them, but it’s the same fungus causing the problem. This is an annular, so that means ring-shaped, scaly plaque with central clearing. You should probably get pictures of these, images of these. I’m trying to put them together on the website. I’m not sure if it’s going to work out, but you’re definitely going to want to take a peek at these to help keep them in your head. You may get images on your PANCE. There definitely are images available, but they’re not constant, right?

They’re not the most common thing. But where the images come in handy is just getting you that picture in your head that you can hold on to. So these are annular scaly plaques with central clearing, a raised scaly border, and they’re typically dry and itchy. So your question stem is just going to be like that, an itchy annular scaly rash with the central clearing, blah, blah, blah, blah, blah. Physical diagnosis is going to be your, the way you diagnose this. Treatment again is going to be your azoles or an oral antifungal if it gets really, really bad. Next we have our parasites.

So we’re going to cover just scabies and lice in this section. Scabies is caused by Sarcoptes scabiei, something like that. Spreads skin-to-skin contact. Clinical finding is intense, pruritic papules or nodules, those linear burrow-like lesions. That’s what is the real key here. It’s not the only place you’ll see linear lesions, but it is a key for scabies involving the finger webs, wrists, axilla, waistline, or genital area. So the question stem will have intense itching with linear burrow-like lesions in the finger webs or wrists is most common.

Your diagnosis here is going to be clinical there is i do remember learning about you use oil immersion from a scraping to look for the eggs and for the for the scabies i’m not sure how many people are actually doing that in their offices at this point i think you probably go ahead and treat it so i’m not sure it’s relevant for your exams treatment is going to be a Permethrin cream, this is a topical antiparasitic. You can do oral ivermectin. And then check on all contacts. That’s important. This is super, super contagious. One of the keys to this also is that it has nocturnal itching is worse. Linear burrow-like lesions, that’s a real key.

Finger webs are classic in the wrists. Good, good, good.

Let’s move on to lice. This is a parasitic infection caused by lice. Most commonly pediculosis capitis is head lice. Our clinical presentation here is scalp itching, really bad itching. You can actually see the nits or eggs firmly attached to the hair shafts. You can see excoriations from all the scratching because this is really, really irritating, which is common behind the ears and around the neck. The question stem may be something like, is scalp itching with visible nits attached to the hair shafts.

Diagnosis is going to be clinical. And one thing to note in your physical exam is that the nits are adherent to the hair. They don’t just flake off. They sort of are glued on there. The treatment again is going to be the permethrin lotion. And then mechanical removal of nits is recommended. Moving right along, let’s go on to our bug bites.

We’re going to start with spider bites. You have two major ones you’re going to have to tell between the brown recluse and the black widow.

So let’s do them sort of as a group. The brown recluse is a necrotic issue, right? Where the black widow is a neurotoxic issue. Brown recluse is often associated with South Central US, you know, not 100%, but if that comes up, that’s certainly a way to go. In the brown recluse, you’re also going to get an early bite. It’s going to be painless or mild because the necrosis develops later. It’s not an initial thing and it causes local tissue destruction where in the black widow you get systemic symptoms are the predominant issue here for the black for the brown recluse and the initial bite is mild but progresses to pain you get a central necrosis with surrounding erythema sounds lovely and a possible eschar formation that’s just like burnt dead looking tissue all black and yuck the question stem here would be a painful bite that develops a central necrosis over hours to days Here you’re going to do local wound care Pain control And really that’s going to be about it There’s not much else to do You’re going to scrape that thing out You’re going to clean it out To try to make sure that that venom Isn’t going to cause any more damage But really it has done what it has done Instead with the black widow Again the bite is going to be minimally painful at first But you can get severe muscle cramping And abdominal pain You can get diaphoresis Hypertension is possible so here you’re going to get severe muscle cramping or abdominal pain after a spider bite is going to be more what your question stem looks like so these should be really easy to tell apart a black recluse and a black widow i’m sorry a brown recluse and a black widow here you’re going to have supportive care muscle relaxants and analgesia and there is an anti-venom if it’s a severe issue so if you’re thinking muscle cramps following a spider bite you’re definitely thinking black widow and again the key is going to be systemic findings versus local findings that necrotic tissue versus muscle cramping, stomach pain, that kind of thing.

Then we move into tick bites. And the big thing for tick bites is, is it a local reaction we’re talking about, or are we dealing with early Lyme disease? That’s really what we want to know. Lyme disease is most common in the Northeast and upper Midwest, where I am. Ticks are rampant, and Lyme disease is part of it. Not now, because it’s January, but over in the spring and summer and fall, certainly. I’m not sure these geographic areas are as important.

Definitely know the rest of the information and then tack that on as sort of a breadcrumb that’s going to help push you in a direction. But not the clear identifier, right? You want to know what the lesions look like, what their paths look like, etc. It’s far more important. For a local reaction, there’s a small erythematous papule at the site of the bite. And it appears almost right away after the tick is removed. It doesn’t expand and it resolves in a couple days.

The patient just needs some reassurance and symptomatic care. Early Lyme disease, you get erythema migrans, which is a characteristic rash of early Lyme. This indicates systemic infection and not a local issue. So what this is, it’s an expanding erythematous rash, usually greater than 5 centimeters. It develops days to weeks after the tick bite. It may have a central clearing, but bullseye is not required. The bullseye rash is the key term for Lyme disease, right?

But it doesn’t have to happen. Just like all of our key terms, like all of our findings here. We talked about herald patches, right? You might have missed it. The patient may not present with it. So you’d like to see it in a test question, but you may not see it in the office. These are usually not painful or pruritic.

So you get this lesion, but it doesn’t hurt and it’s not itchy. Management here is going to be, you’re going to treat it clinically. Without waiting for labs because you have concerns. So you’re going to give doxycycline. And then one place that I would know, I don’t spend a ton of time on things like if you’re pregnant or if you’re allergic or all of those things. I think they’re important. I think they matter.

But I think getting the foundation is more important. And then we add those pieces later. In this case, I would include amoxicillin if pregnant or a child. I just feel like that’s a question that can come up because it’s so common in children. Who are playing outside, etc. And can pick up ticks with Lyme disease. So something I would definitely consider.

So that expanding rash is erythema migrans. This is early Lyme disease. Don’t have to wait for serologies. Get them some doxycycline. I have two left with bees and wasps and then bedbugs and fleas and then we’ll wrap it up for today. Don’t worry, next week we’re going to get into childhood exanthems. You’re going to love that.

Bugs and fleas. I’m sorry, let’s start with bee wasps things. Clinical presentation is pain, erythema, and swelling at the local site. Now you can get a systemic reaction with urticaria, wheeze, and hypotension. Obviously, that’s concerning. That’s when we’re talking about an anaphylactic reaction instead of just a local issue. The local issue is not a big deal, right?

Some ice, you treat it mostly by consoling the child who was walking barefoot and stepped on a bee. You console them, but generally speaking, not a huge deal. Obviously, if you have multiple stings, multiple things, you may want to get an antihistamine, but what we’re really concerned about is that anaphylaxis, the hives, wheezing, hypotension, that kind of thing, in which case you’re going to treat with epinephrine because you’re worried about their airway. Bedbugs and fleas. Clinical presentation here is grouped or linear pruritic papules. So again, this is kind of similar to our scabies because you get those linear pruritic papules. This is often on exposed skin, history of travel, bedding, or pets, et cetera.

You’re going to do symptomatic treatment and environmental controls. So environmental controls are wash everything, right? Burn things, et cetera, until you can get rid of these. Here, there’s no systemic illness, nothing else going on here. You just need to really, really clean the area, and that’s really the issue. It’s less of a treat the person as it is treat the environment.

All right, let’s talk about our exam summary for this whole section. I mean, just the section on bites. If you see necrosis, you’re thinking brown recluse. If you’re seeing muscle cramps, you’re thinking black widow. If you’re seeing expanding rash after a tick bite, erythema migrans, you’re thinking Lyme disease. Hypotension, wheezing after a sting, you’re thinking anaphylaxis and you’re scared, so you’re getting the epinephrine. Linear itchy bites overnight, bedbugs, fleas, but also we were talking earlier about scabies, so keep that in mind.

Excellent. Well, that’ll bring us to the end of this section. I’m glad I decided to bump viral infections to next week. I was going to cover it all today, but it just seemed like it was going to be a lot to hold on to, a lot to parse out. The rashes, and certainly the rashes are going to matter though, right? Because your cellulitis, your erysipelas, your impetigo are going to look, might look like your exanthems. So we’re going to try to bounce back and forth and make sure that we understand how those all fit together and how to separate them when we cover all this next week.

For this week, our study tip is actually going to be really straightforward and simple. I’m going to be hosting a Master Class called PANCE Game Plan. This is a PANCE Game Plan session. So we’re going to be planning out how to get ready for your PANCE. I’m going to cover a 33 Days content calendar, explain how I set up a content calendar so that you can keep moving forward and keep working and feel like you’re getting to everything. What I’m finding is too many people are not having a plan when they go after the PANCE, not having a plan when they’re working on their end of rotation exams, not having a plan when they’re going to their next big test or the EOC. They’re grabbing whatever they find on Reddit, and that’s not good enough.

I want you to develop a plan, so that’s what we’re going to be. That’s part of what we’re going to be doing. The other thing we’re going to be doing, which I have never done before is I’m going to walk through a five-part score stack system for just how to sit down and study a specific topic. So in part one, we’re going to go through the calendar, exactly what topics to cover on what days, how to make that work into your schedule as you get ready for your next big exam. Then I’m going to show you exactly what I would do if I were sitting down to take the PANCE and what I would be doing during each study session very, very specifically. And then finally, I’m going to give you my anxiety-proof exam protocol. So I’ll walk through of what to do to help calm your nerves both before and during your exam.

Make sense? So I’m really excited about this program. I’m not going to do a study tip today because that’s when it’s going to be filled with study tips. So I want you, in fact, the five-part score stack system is nothing but how to set up your study system. So I’m going to skip that for today. Registration for that is open. They’re going to be two nights, January 15th, I think is a Thursday at 8 p.m.

And then the following Monday, which I think is the 19th, also at 8 p.m. To make it as easy as possible. You can register for that at physicianassistantexamreview.com/masterclass. We’ll take you right to that page. Please share this with your friends, with your other members of your cohort, with your faculty, anyone who you think might need some help getting ready for the PANCE, which is maybe everyone, and put this out there. I think it’s going to be really, really valuable. You’re going to get a ton out of it.

You’re going to get people to thank you for pointing them in this direction. So that’s going to be our study tip for today.

All right, let’s hop into our priming questions and round this show out. Poorly defined erythema and swelling on one shin suggests what diagnosis? These should be easy now, right? Because we just covered them. When we mix them in down the road, they get hard, but initially they should be easy. So this is when you want to start locking these in. Poorly defined erythema swelling on one shin suggests what diagnosis?

Cellulitis. Beefy red rash with satellite lesions suggests what infection? Candidiasis an annular scaly rash with central clearing suggests what organism type? This is a dermatophyte tinea infection intense nocturnal scratching with linear lesions on the finger webs suggests what infestation? So because I said finger webs you’re thinking scabies but I could see where you might wind up with fleas or bed bugs how should an expanding erythematous rash after a tick bite be treated your answer here is doxycycline or amoxicillin if they’re pregnant or a child beautiful work excellent job today if this helps us all help here’s the helped here’s the important takeaway this isn’t about memorizing facts that’s not what we’re doing here it’s about knowing what to notice how to organize it and how to think under pressure think different work different score different that’s our motto that’s what i want for you that’s why we go through the material in the way that we do. It’s why we take the notes in the way that we do. We don’t just teach the content, we teach how to learn it, how to study it, how to hold on to it, and then how to have it show up for you on the day when you need it.

Again, don’t forget to register for that Master Class physicianassistantexamreview.com/masterclass, where I’m going to cover a step-by-step content calendar to keep you on track, a what to do when you sit down to study, my five steps for doing that, and then finally an anxiety-proof protocol so that you can make sure that you’re walking into your exams and showing up as the best possible version of yourself so that you can get the scores you know that you deserve. One more time, I’m just going to remind you, please share this with a friend, share this with your faculty, have them put it out. It’s going to be really, really valuable. And I look forward to talking to you about childhood exanthems next week.

All right, take care. Thank you.