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A 7-month-old male is brought to clinic for a "rash all over." Six weeks ago, his parents noticed him rubbing his legs against his crib and scratching his head frequently. They are concerned because they find blood on his sheets in the morning, and he has become increasingly irritable. He is eating and drinking normally. His past medical history is unremarkable. His father has sensitive skin and hay fever, but no one else in the family currently has a rash. He does not attend a daycare. On skin examination, you find lichenified and erythematous patches of skin with fissures and bleeding on the ventral heels, dorsal feet, hands, and a few areas on the scalp. His cheeks are bright red with scale. His diaper area is uninvolved and there are no lesions in the web spaces of the hands and feet.
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Question 17.2.1 Based on the description, which of the following is the most likely diagnosis?
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Answer 17.2.1 The correct answer is "B." The most likely diagnosis is atopic dermatitis, also known by the moniker eczema. Atopic dermatitis is characterized by an intensely pruritic eruption of the skin with associated dryness. A red rash subsequently develops. Atopic dermatitis is often referred to as the "itch that rashes." It occurs in characteristic locations. In younger infants, the cheeks and neck are involved. As they begin to crawl, their extensor surfaces are involved. The diaper area, because it is moist, is not usually involved. In older children, the flexural areas, such as the antecubital and popliteal fossae, are involved. Seborrheic dermatitis ("A") is common in infants (cradle cap) and is usually seen on the scalp and face, although it can involve the whole body. Seborrheic dermatitis is usually associated with a yellow, greasy scale and is less erythematous than atopic dermatitis. Scabies ("C") typically affects certain locations (web spaces, wrists, waist, etc.) and uncommonly involves the scalp, except in infants or immunocompromised patients. Also, in this question, he does not appear to have any exposure to scabies. Tinea corporis ("D") presents with a ring of advancing erythema and a central clearing ("ringworm"). Finally, tinea versicolor ("E") typically involves the trunk and extremities with hypo- or hyperpigmented patches with superficial scale. It does not involve the scalp, and is not very pruritic.
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You diagnose the patient with atopic dermatitis.
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Question 17.2.2 Which of the following is true about atopic dermatitis?
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A) The prevalence of atopic dermatitis appears to be decreasing worldwide
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B) Atopic dermatitis tends to worsen with use of emollients
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C) In some patients, skin infections can exacerbate atopic dermatitis
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D) Positive skin prick tests and RAST testing correlate highly with food challenges (e.g., those with positive tests will have worsening of their rash when given a food challenge)
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E) In most infants, atopic dermatitis will not significantly improve or resolve by school age
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Answer 17.2.2 The correct answer is "C." Skin infections (Staph or Strep infections) can be associated with worsening atopic dermatitis, and when children flare, impetiginization (superinfection) should be considered. In these situations, a course of antibiotics may improve the overall clinical course (cephalexin is often a good choice). Sixty percent of atopic dermatitis appears in the first year of life, usually after 2 months of age; and it will usually get somewhat better by school age. The cause of atopic dermatitis is not yet known. The role of specific allergens is controversial. In some patients, a food allergy can worsen the disease but is not thought to be the cause. However, in severe, unresponsive atopic dermatitis, food allergens should be evaluated. Most patients who have positive allergy testing to foods do not have improvement in their skin with removal of the allergen. Atopic dermatitis does tend to improve as the affected child ages ("E"), and the use of emollients ("B") is a cornerstone of therapy.
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HELPFUL TIP (OR NOT):
The link between allergies of any kind, including food and environmental, and atopic dermatitis has been called into question. It does seem that a subset of patients have atopic dermatitis that flares in response to exposure to certain food and environmental triggers, but these patients are the minority. Random elimination diets are to be discouraged. Only patients with proven food allergy and an immediate worsening of symptoms when exposed to that food should eliminate that particular food from their diet.
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Question 17.2.3 The clinical features of impetiginized atopic dermatitis include:
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A) Lichenification of the skin
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B) Pruritus and relapsing nature
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C) Associated asthma or allergic rhinitis
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D) Elevated IgE serum levels
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E) Redness of the skin with honey-crusting
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Answer 17.2.3 The correct answer is "E." Although all of the above can be associated with atopic dermatitis, honey crusting implies a secondary bacterial infection (impetigo), which is common in atopic dermatitis and needs to be recognized and treated to get atopic dermatitis under control. Oral antibiotics and chlorinated baths can be used to help control the superinfection. Waxing and waning pruritus is what defines this common skin condition. Chronic scratching often leads to thickened skin with accentuation of skin lines (lichenification). Early lesions will not have lichenification, however. Asthma and allergic rhinitis can be associated with atopic dermatitis. This common hypersensitivity triad is referred to as atopy (although atopic dermatitis is not allergic in nature). "D," elevated IgE, does occur in patients with atopic dermatitis, and higher levels of serum IgE are associated with more extensive disease of greater chronicity. However, an elevated IgE level is merely an association and is not pathognomonic of atopic dermatitis. Erythema of the skin is a nonspecific sign of inflammation and is seen in many skin disorders.
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Question 17.2.4 Your initial recommendation should include which of the following in the management of atopic dermatitis:
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A) Daily use of thick emollients such as white petrolatum
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B) Bathing with lukewarm water and mild cleansers
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C) Topical corticosteroids or topical immunomodulators
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D) Oral antibiotics if there is evidence of superinfection
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Answer 17.2.4 The correct answer is "E." The protective barrier of the skin is broken down in patients with atopic dermatitis. By frequently applying a protective barrier, such as petrolatum, the skin becomes less pruritic resulting in less itching-induced skin trauma and rash, thus decreasing the "itch-scratch cycle." This is the most important aspect of long-term management. Topical steroids and immunomodulators work well to decrease the inflammation in the skin and are first-line anti-inflammatory treatment; however, the goal is to protect the skin with thick emollients so that the skin does not dry out and itch, leading to scratching and subsequent inflammation. Daily bathing with mild cleansers and cool water followed by the application of emollients is recommended. Patients with atopic dermatitis have a higher bacterial count of Staphylococcus aureus on their skin. By bathing for short periods daily, the bacterial count is decreased, thus decreasing the risk of secondary infection. Oral antihistamines cause some level of sedation, which is often helpful at night when the child is awake and itching. Interestingly, there is almost no evidence to support the use of antihistamines in the treatment of atopic dermatitis, except small studies that have shown nonsedating antihistamines to be no better than placebo. If you choose to recommend an antihistamine, use an older drug (e.g., diphenhydramine) but use extreme caution in children under 2 years of age—there is no proven benefit for any indication in this age range and infants are more sensitive than adults and older children to the CNS depressant effects of diphenhydramine. "E" is incorrect. However, oral antibiotics may be necessary if there is extensive impetigo. Finally, bacteria can lead to a flare of atopic dermatitis. Occasionally, treatment with antibiotics may be of benefit (more below).
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HELPFUL TIP:
Mid-potency steroid (e.g., triamcinolone) ointments are the mainstay of pharmacotherapy for atopic dermatitis flares. For the face, low-potency steroid (e.g., hydrocortisone) ointments can be used for a maximum of 2 to 3 weeks at a time. For severe, acute flares, systemic steroids can be employed for 10 to 14 days.
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HELPFUL TIP:
Topical calcineurin inhibitors (e.g., tacrolimus, pimecrolimus) are second-line therapies in the treatment of atopic dermatitis. Although they are generally safe and well tolerated, they are expensive and carry a "black box warning" related to possible cancer risk. There are a few reported cases of lymphoma and cutaneous cancers developing in humans using topical calcineurin inhibitors. Animal studies support this association. They are contraindicated in patients younger than 2 years.
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A recent ear infection has caused your patient's skin to worsen. He returns to clinic and your physical examination reveals the skin lesion seen in Figure 17-2. He has appreciably enlarged cervical lymph nodes. The patient has no known drug allergies.
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FIGURE 17-2. (Courtesy of Drs. Karolyn Wanat and Megan Noe.)
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Question 17.2.5 Which of the following oral antimicrobials would be the best initial choice for this patient?
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E) No systemic treatment is necessary at this time
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Answer 17.2.5 The correct answer is "A." Patients with atopic dermatitis are prone to certain skin infections that may exacerbate their disease. Ninety percent of patients with atopic dermatitis will grow S. aureus on swab cultures of their crusted lesions. By decreasing the bacterial count, inflamed lesions often heal faster. Depending on your community susceptibilities, community-acquired methicillin-resistant S. aureus (CA-MRSA) may be of concern. However, first-generation cephalosporins are a reasonable initial antibiotic choice for impetiginized atopic dermatitis because of excellent skin penetration and activity against Gram-positive cocci (both Staph and Strep). Tetracycline is another option for impetiginization; however, this should be avoided in young children, as should fluoroquinolones (except in rare cases such as cystic fibrosis). Systemic therapy is necessary at this time due to clinical worsening and presence of lymphadenopathy.
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HELPFUL TIP:
Patients with head and neck atopic dermatitis may benefit from systemic antifungal therapy (e.g., itraconazole) for a month. Malassezia yeast is a common skin flora found to cause an inflammatory reaction in patients with head/neck atopic dermatitis, and its eradication may improve atopic dermatitis symptoms in these patients. The evidence is pretty weak, so save it for third-line treatment in patients with more severe symptoms.
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Your patient's culture results are consistent with methicillin-sensitive S. aureus (MSSA). With the appropriate antibiotics, the patient improves markedly. Time to rest on your laurels … Wait … there's this little thing called continuity of care, and 3 months later, your patient returns with a new eruption. Clinical appearance is shown in Figure 17-3.
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Question 17.2.6 Which of the following is the most appropriate treatment at this time?
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Answer 17.2.6 The correct answer is "E." Patients with eczema may also develop eczema herpeticum, a particularly severe form of disseminated herpes simplex with punched out erosions and rapid spread of HSV within the areas of eczema. Patients can develop both eczema herpeticum and impetiginization, so treatment of both is important. The characteristic look of punched out erosions requires immediate therapy with acyclovir, and often requires intravenous medications. These patients should be treated immediately with antivirals as the disease may be fatal. Treatment with cephalexin in addition should be utilized, especially because the patient improved previously.
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As the patient grows, he improves significantly. However, his skin continues to be sensitive to many products. As a teenager, he presents with a recurring rash near his wrist that is intensely pruritic. He has recently started wearing a bracelet … and he won't take it off despite the rash because he's too cool … even though it seems to be a girl's bracelet (see Fig. 17-4).
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Question 17.2.7 The test most likely to confirm your presumptive diagnosis is:
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A) Potassium hydroxide (KOH) of a skin scraping
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D) Serum thyroid-stimulating hormone level
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Answer 17.2.7 The correct answer is "C." The patient most likely has an allergic contact dermatitis to the nickel in the metal bracelet on his wrist. Patients with a history of atopic dermatitis are more likely to have contact hypersensitivities. Nickel is a common contact allergen and can also be seen with contact to earrings, optical glasses, and buttons on jeans. Patch testing is a test for reactions to delayed-type hypersensitivity reactions that can identify many of the common contact allergens in the skin. KOH application to a skin scraping is used to identify fungal elements. KOH dissolves keratin, the protein in skin, to better identify the fungal elements. Tzanck preparations stain blister scrapings to evaluate lesions suspicious for herpes or varicella viruses. Thyroid disease can cause many skin conditions but is not a known cause of allergic contact dermatitis. An abnormality in the TSH level is least likely to yield a diagnosis in this case. As to "E," serum IgE levels may be elevated in atopic patients, but this is not diagnostic as IgE can be elevated in many states.
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Objectives: Did you learn to…
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Recognize atopic dermatitis by its classic presentations?
Identify the hallmarks of atopic dermatitis?
Manage a patient with atopic dermatitis and its complications?
Recognize that eczema herpeticum in those with atopic dermatitis?