Applied Evidence

Derm diagnoses you can’t afford to miss

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Innocuous or serious? Patients’ lives may depend on your ability to recognize dangerous dermatologic conditions.



Practice recommendations
  • Management of hereditary angioedema should include fresh frozen plasma containing C1 inhibitor (C1-INH), whenever possible; if C1-INH-containing plasma is unavailable, fresh frozen plasma can be used instead (SOR: A).
  • Do not give neomycin to patients with suspected cellulitis; the drug may promote antibiotic resistance in Staphylococcus aureus, a pathogen often associated with this condition (SOR: A).
  • Whenever a patient presents with erythematous skin lesions and a recent history of receiving penicillin or a cephalosporin antibiotic, a sulfa derivative, or an anticonvulsant, the suspected medication should be stopped until Stevens-Johnson syndrome is ruled out (SOR: A).

Strength of recommendation (SOR)

  1. Good-quality patient-oriented evidence
  2. Inconsistent or limited-quality patient-oriented evidence
  3. Consensus, usual practice, opinion, disease-oriented evidence, case series

Skin eruptions are a common reason for visits to primary care physicians. While most are innocuous, some are associated with—or are early warning signs of—severe allergic reactions or other emergent conditions. A 9-year-old patient I’ll call Julie is a case in point.

The first time Julie’s parents brought her to our clinic, she’d been complaining of a sore throat and had a fever that hovered between 102° and 103°F for several days. The physician who examined Julie found mild maxillary tenderness. A rapid streptococcal throat swab was negative; her doctor prescribed a 10-day course of trimethoprim/sulfamethoxazole (TMP/SMX) for presumed acute sinusitis.

Thirteen days later (3 days after the patient completed the course of antibiotics), Julie’s parents brought her back to the clinic. Her throat still hurt, and she had erythematous oval lesions on her trunk and upper extremities. Her physician diagnosed scarlet fever and wrote a prescription for penicillin.

The following day, Julie was taken to the emergency department (ED) with bilateral conjunctival hyperemia and diffuse, confluent erythematous macules throughout her body. The ED physician who examined Julie found a 2.5 × 2.0 cm targetoid lesion with a necrotic, purpuric center on her lower back—a diagnostic clue to the cause of her signs and symptoms.

If you had been Julie’s physician, would you have been alert to that clue?

For family physicians accustomed to seeing relatively mild skin disorders, recognizing and responding to dermatologic conditions with potentially dire outcomes can be challenging. This review, and the images that accompany it, will help you sharpen your dermatologic diagnostic and treatment skills, both for benign disorders and those that are less common and more severe. We’ll also tell you more about Julie and her diagnosis.

Urticaria: A simple case of hives?

This common allergic reaction affects close to 10% of the population at some point in their lives. The affected areas are itchy and have raised, circumscribed red welts with surrounding erythema.1 Urticaria can occur throughout the body, with new lesions often erupting as the old ones disappear.2,3

Despite the persistent itchiness that patients typically complain of, however, urticaria is usually self-limiting, and rarely life-threatening. Acute urticaria normally resolves within 2 to 6 weeks.2,4

In most cases, urticaria arises secondary to exposure to an allergenic substance, chemical, or emotional stress.4,5 In rare instances, systemic diseases, such as hematologic malignancies, can also cause urticarial lesions to erupt throughout the body.4

Body piercing, cosmetics, latex exposure, Helicobacter pylori, insects, and angiotensin-converting enzyme (ACE) inhibitors have been identified as common triggers of urticaria, as have nonsteroidal anti-inflammatory drugs (NSAIDs) and antibiotics, animal dander, and foods such as shellfish, nuts, and dairy products.4,6

Treatment of all forms of urticaria should be based on identification and strict avoidance of the causative agent, if it’s known.7 Following withdrawal of the specific agent, symptomatic treatment with medications such as histamine antagonists and corticosteroids remains the mainstay of therapy.4,8 A daily dose of 40 to 60 mg prednisone for 5 days is a reasonable therapeutic regimen for adults; a 5-day course of 1 mg/kg per day is suitable for pediatric patients.4,8,9

In the event that topical or oral therapy is ineffective in mild cases of urticaria, intravenous (IV) diphenhydramine (50 mg) can be administered every 6 to 8 hours.4,8 IV diphenhydramine typically takes 30 minutes to work, while corticosteroids take at least 2 hours to reach full effect.4,8

In an emergency setting, subcutaneous epinephrine (0.3-0.5 mg) can be useful in treating severe urticaria.4,8 And recent clinical trials have demonstrated complete clearance of urticaria with leukotriene inhibitors, such as montelukast (10 mg).10


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