Approach to common skin rashes: Clinical sciences

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Introduction0:00–0:53

A skin rash is an area of irritated or inflamed skin that reflects the body's reaction to a localized or systemic process.
It can result from external contact exposure or an internal process causing immune dysregulation or infiltration of inflammatory cells.
It's important to first identify if an adverse medication reaction is the cause of your patient's rash as this might be potentially life threatening.
Other possible diagnoses include infectious causes such as folliculitis, scabies, shingles and tinea corporis and inflammatory or autoimmune causes such as atopic dermatitis, contact dermatitis, seborrheic dermatitis, acne vulgaris, rosacea and psoriasis.
Now, if your patient presents with the skin rash, first, perform a focused history and physical examination, your patient will report a rash that might be red itchy scaly or painful.

Stable0:53–1:24

The physical exam will reveal a rash that might be erythematous, macular papular vesicular or comprised of discrete plaques at this point.
Diagnosed dermatitis, a nonspecific diagnosis that indicates inflammation of the skin. Next assess for a cutaneous adverse medication reaction.

Cutaneous adverse medication reaction1:24–3:14

These patients report a widespread rash that appeared in as little as one day and up to three weeks after starting a medication such as an antibiotic, NSAID or antiepileptic.
The physical exam will show an erythematous maculopapular eruption and there might be dark red or purpuric macular lesions or urticaria.
With these findings diagnose cutaneous adverse drug reaction. Here's a clinical pearl urticaria, better known as hives is a common, usually self limiting skin reaction triggered by medications.
Certain foods allergens or stress symptoms include itchy, raised red wheels, also known as welts on the skin surface. Acute urticaria may progress rapidly to life threatening angioedema or anaphylactic shock.
The mainstay of treatment is avoiding further exposure to the suspected trigger. Here's another clinical pearl cutaneous adverse drug reactions that carry significant risk for complications or even death include anaphylaxis, Stevens, Johnson syndrome, toxic epidermal necrolysis, acute generalized exanthematous pustulosis and drug reaction with eosinophilia and systemic symptoms, otherwise known as Dress Syndrome.
So always do a thorough review for new medications and have a high index of suspicion if your patient's rash is not improving or is worsening.

Infectious Causes3:14–3:25

On the other hand, if a cutaneous adverse medication reaction is not present, your next step is to assess for infectious causes of a skin rash.

Folliculitis3:25–4:18

First up is folliculitis. Your patient will report an itchy rash on hair bearing regions of the skin as well as a recent increase in sweating.
They might also report hot tub or swimming pool exposure or recent use of topical steroids. The physical exam will reveal papules and pustules around hair follicles with perifollicular erythema with these findings diagnosed folliculitis.
Here's a clinical pearl more severe cases of folliculitis may lead to cellulitis. An infection of the deeper skin tissue where the skin is erythematous, edematous, warm to the touch and tender to palpation.
If your patient's rash is worsening, they might be developing cellulitis and will need antibiotics. Let's move on to scabies.

Scabies4:18–5:31

These patients report a severely itchy rash that's worse at night and they may have a history of inadequate access to hygiene or poor nutritional status.
Physical exam will reveal serpiginous burrows with erythematous papules and vesicles most commonly in the hands, feet, wrists and elbows with these findings, diagnose scabies.
Here's a clinical pearl scabies is typically a clinical diagnosis. But if you're unsure, you can perform dermoscopy or obtain skin scrapings.
Dermoscopy will reveal burrow structures and on skin scrapings. You can visualize mites.
And here's another clinical pearl. Regardless of symptoms, all close contacts of patients with scabies should receive treatment with topical permethrin.
Moreover patients and contacts should decontaminate bedding, towels and clothing when receiving treatment to prevent reinfection.

Shingles5:31–6:22

Next, let's discuss shingles. Patients may sometimes start with a prodrome of fever and malaise but more commonly, the first sign is skin pain and tingling followed by a painful localized rash.
The physical exam will show a unilateral papulovesicular rash isolated to a specific dermatome at this point. Consider shingles and test the vesicular fluid with a zinc smear a polymerase chain reaction or PCR or a direct fluorescent antibody or DFA test or you can order a varicella zoster I GM blood test if the zinc PCR or DFA are positive or if the varicella zoster I GM is positive diagnose shingles.
Keep in mind that a shingles diagnosis can often be made based on clinical findings alone. Next up is tinea corporis.

Tinea Corporis6:22–7:08

These patients typically report an itchy red rash. Typically on the neck trunk or extremities.
Physical exam will reveal single or multiple annular or ovoid patches, sharp margins with an erythematous scaly edge and a ring shape with central clearing.
With these findings considered tinea corporis obtain skin scrapings and perform a Koh test. If the KO H test reveals septate and L hyphae diagnose the dermatophyte infection called tinea corporis.

Inflammatory/Autoimmune Causes7:08–7:17

A fungal culture can be done if the Koh test is negative or inconclusive or if the presentation is unusual. Keep in mind that the diagnosis of tinea corporis can also be made on clinical findings alone.

Atopic Dermatitis7:17–8:24

Ok. Now, if infectious causes of a skin rash are not present, assess for inflammatory or autoimmune causes.
First up is atopic dermatitis, better known as eczema. Your patient will report an intensely itchy red rash and may have allergic rhinitis, asthma or food allergies.
Physical exam in infants and Children will show dry erythematous scaly patches with lichenification on the cheeks or flexural surfaces of the skin such as the antecubital fossa.
On the other hand, adults will have lichenified lesions mostly on the hands. With these findings diagnose atopic dermatitis.
Here's a high yield fact, atopic dermatitis is part of the atopic triad comprised of atopic dermatitis. Allergic rhinitis and asthma, which may start simultaneously.

Contact Dermatitis8:24–9:28

These patients have a defective barrier of the skin which allows irritants and allergens to penetrate and cause inflammation via an overactive helper T cell response which kicks in during an adaptive immune response.
Next up is contact dermatitis. Your patient will report an itchy burning rash most commonly on the hands.
There might be a history of chemical metal or topical medication exposure. Physical exam will reveal erythema, oozing, crusting, tender vesicles or pustules along with hyperpigmentation and lichenification with these findings diagnose contact dermatitis.
Here's a clinical pearl to keep in mind, many different substances can cause contact dermatitis including jewelry, cosmetics, fragrances and plants.
Nickel is a common metal associated with contact dermatitis. Your patient should avoid the suspected substance and the rash should improve within 2 to 4 weeks.

Seborrheic dermatitis9:28–10:21

If there's no improvement, your patient might need patch testing which consists of placing different common allergens on the skin and observing for a skin reaction.
Let's move on to seborrheic dermatitis. These patients will report an itchy rash on the scalp, face and chest.
They may have a history of immunodeficiency or neuropsychiatric disorder or they may report exposure to certain medications such as dopamine antagonists and immunosuppressants.
Physical exam shows salmon colored papules and plaques with white, fine scales with a yellowish crust. With these findings diagnose seborrheic dermatitis.

Acne Vulgaris10:21–11:10

Here's a high yield fact, seborrheic dermatitis along with atopic dermatitis and contact dermatitis is characterized by a relapsing and remitting pattern with potential devastating impact on quality of life.
Next up is acne vulgaris. These patients will report pimples on their face, chest back and arms.
They may also have certain triggers such as stress hormones, medications and diet. Physical exam will reveal open and closed Coomes, papules, pustules and possibly nodules, cysts or scars with these findings diagnose acne vulgaris.

Rosacea11:10–11:50

Here's a high yield fact. Cutibacterium acnes.
Formerly propionibacterium acnes is a bacterium within the normal microbiome of the skin that can trigger the inflammatory response observed in acne vulgaris.
Ok. Moving on to rosacea, your patient will report pimples, flushing and redness on the nose, chin, cheeks and forehead.
They may also have eye symptoms like dryness, tearing and burning. Physical exam will show central facial erythema and there might be papules and pustules, telangiectasias as well as ocular manifestations such as conjunctival infection and corneal infiltrates, rhinophyma or a nose that becomes red, bumpy and enlarged may also be present with these findings.

Psoriasis11:50–11:50

Psoriasis11:50–12:34

Diagnosed rosacea last up is psoriasis. These patients will report an itchy scaly rash on the knees, elbows, arms, scalp or back.
The rash tends to be better in the summer and worse in the winter. Physical exam reveals erythematous plaques covered with silvery scales over extensor surfaces.
With these findings diagnose psoriasis. Here's one last high yield fact, keep in mind that patients with psoriasis might also have psoriatic arthritis.

Review12:34–13:39

They'll typically report painful inflammation of the joints leading to sausage shaped, swelling of the fingers and toes known as dactylitis.
All right, as a quick recap. A skin rash is a common presentation in the primary care setting.
With causes ranging from benign to life threatening, immediately identify the most serious cause a cutaneous adverse medication reaction.
If an adverse medication reaction is not present, assess for infectious causes such as folliculitis, scabies, shingles and tinea corporis.
If infections aren't present, evaluate for inflammatory or autoimmune causes such as atopic dermatitis, contact dermatitis, seborrheic dermatitis, acne vulgaris, rosacea and psoriasis.