Localized Rashes: Impetigo, Cellulitis and Herpes Zoster

by Charles Vega, MD

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    00:01 Impetigo and cellulitis, so this is an infection of the superficial skin structure down into the dermis.

    00:08 That's the difference.

    00:09 But they are – they appear very similarly.

    00:12 Pain, tenderness, calor, erythema, those are the hallmarks of both of these.

    00:16 But impetigo is more superficial.

    00:19 And I have a hard time sometimes differentiating between the two just based on what I'm seeing in front of me in clinic.

    00:26 The important difference in treatment is mild impetigo could be treated with topical antibiotics alone, which is great.

    00:32 So, if it seems very – it’s not very – there’s not a lot of calor.

    00:35 The pain is not that severe.

    00:37 It’s just a red area.

    00:37 It doesn't bother the patient a lot.

    00:39 That one might be conducive to using topical antibiotics.

    00:44 But because they are so related, it can be difficult to differentiate them.

    00:49 If there's a question, I'm likely to treat it with oral antibiotics.

    00:53 I don’t see a ton of cases of either of these conditions either.

    00:55 So, therefore, I also have a lot of high-risk patients with things like diabetes and heart failure and other other types of comorbidities that can make these infections more likely to spread.

    01:08 So, therefore, I'm more aggressive at treatment.

    01:12 And I am aggressive when it comes to the potential for methicillin-resistant staph aureus (or MRSA).

    01:18 If there is somebody who has frequent healthcare contact or certainly with a history of MRSA in the past, I’m going to treat them with a different set of antibiotics.

    01:26 Maybe for a patient who is naïve, for a child for example, that child might receive cephalosporin, usually first-generation.

    01:36 But for the patients like mine who have all those comorbidities, go to the doctor a lot, get admitted to the hospital, sometimes are in a rehabilitation center or nursing home, clindamycin, trimethoprim/sulfamethoxazole could be good options for them because that will handle the MRSA more effectively.

    01:53 And just a warning, always be cognizant of the fact that cellulitis can progress into an necrotizing fasciitis.

    02:02 A necrotizing fasciitis can masquerade initially as just a simple cellulitis.

    02:07 So, patients who feel really sick, who have a rapid progression of their rash, who have other evidence like neurovascular or neurological changes that suggest infection in deeper layers, compartment syndrome, those are patients you want to stay on top of and refer urgently.

    02:25 Don't wait to send them to the emergency department for a surgical referral.

    02:30 Do it right now.

    02:34 So, moving on to zoster, and this just – the figure there shows the progression of shingles or zoster.

    02:41 It’s related, of course, to the varicella virus, which sits in your dendrites dormant.

    02:47 And once it's awakened, it travels up nerve fibers and creates its blistering rash.

    02:53 Again, just like it did when the kid got chickenpox like many years ago, zoster comes back.

    03:02 So, the key with herpes zoster is the dermatomal distribution because it is related to those nerve fibers, so that's what separates it from other types of blistering rashes.

    03:11 It’s usually found over this thoracic dermatome, but one important factor is that if it – don't be shocked if it crosses the midline.

    03:19 About one in five cases do, but it should stay dermatomal as well.

    03:24 Post-herpetic neuralgia can be absolutely debilitating.

    03:27 Luckily, it's still uncommon, but certainly it does happen.

    03:32 About 13% of cases of herpes zoster develop post-herpetic neuralgia.

    03:37 More common as patients grow older.

    03:40 So, luckily, we can prevent both herpes zoster and post-herpetic neuralgia as well.

    03:47 And that's with the application of the varicella vaccine or the shingles vaccine.

    03:52 Now, this is a one dose vaccine given at age 60.

    03:54 It’s recommended by the US Centers for Disease Control and Prevention.

    03:58 And it is effective in preventing zoster.

    04:01 It's actually more effective though in preventing post-herpetic neuralgia.

    04:05 So, we can cut the cases of post-herpetic neuralgia by about two-thirds compared with no vaccination.

    04:11 Once you see a case of zoster in your clinic, prescribe antiviral agents, there are a number out there that are all effective.

    04:18 So, it's really based on dosing, as to which one you prefer.

    04:22 That can reduce the duration of symptoms.

    04:24 It also reduces viral shedding, but it's important to get it on board early.

    04:29 Most patients, in my experience, do come in fairly early with this because they are concerned, it hurts for one thing and, therefore, they want pain relief from the pain of the shingles, but they also want to get treated and that improves things.

    04:43 Very important to keep these patients while they have the active lesions away from young children, away from pregnant women who could be at special risk if they contract varicella and also anybody who's immunocompromised.

    04:59 Corticosteroids have been used for the management of herpes zoster.

    05:04 They don't seem to be effective.

    05:05 And because they have a lot of side effects even in a short course, they are not routinely recommended.

    05:11 All right.

    05:12 So, that just took you through some localized rashes.

    05:15 And hopefully, you have a good sense of how to treat them.

    05:18 And I guess my question is, how itchy do you feel right now? Don't worry.

    05:23 You'll be fine.

    05:24 And just use some emollients and we’ll see you next time.

    About the Lecture

    The lecture Localized Rashes: Impetigo, Cellulitis and Herpes Zoster by Charles Vega, MD is from the course Acute Care. It contains the following chapters:

    • Impetigo and Cellulitis
    • Herpes Zoster

    Included Quiz Questions

    1. Systemic antiviral therapy
    2. Topical corticosteroids
    3. Systemic antibiotics
    4. Topical antibiotics
    5. Persistent emollient application
    1. It never crosses the midline
    2. It follows dermatomal distribution
    3. It arises from migration of virus from the nerve dendrites
    4. It is most common on the thoracic region of the body
    5. It is a vesicular rash
    1. Vaccination at the age of 60
    2. Antiviral treatment within the first 72 hours
    3. Topical corticosteroids
    4. Oral corticosteroids
    5. Topical lidocaine
    1. Systemic antibiotic coverage to include MRSA
    2. Systemic antibiotic coverage for normal skin flora
    3. Topical antibiotic treatment for impetigo
    4. Ultrasound to rule out abscess
    5. Referral to surgeon for debridement of likely nectrozing fasciitis

    Author of lecture Localized Rashes: Impetigo, Cellulitis and Herpes Zoster

     Charles Vega, MD

    Charles Vega, MD

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