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Rash, swelling in a 2-year-old febrile girl
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A 2-year-old girl presents to your office with fever and rash. She has had fever (Tmax 101.6°F) for 2 days. The rash began the day before presentation. It started as “red spots” on the legs, then spread. The patient has been itchy and fussy. Today she refused to walk, and her parents noticed her feet, as well as her hands, were swollen. Review of systems is notable for rhinorrhea. She does not take any medications and is otherwise healthy.
Physical examination shows numerous erythematous annular and arcuate plaques (Figure 1). Some of the annular plaques have dusky centers (Figure 2). The patient also has edematous hands and feet (Figure 2).
Figure 1: Annular and serpiginous, edematous, transient erythematous plaques on the patient’s leg. Figure 2: Annular erythematous plaques, some with dusky centers, on the patient’s abdomen. Note that her hand is edematous and her proximal left thigh shows faint erythematous patches where lesions of UM have resolved.
Image: Perman MJ
Diagnosis: Urticaria multiforme
Urticaria multiforme, also known as acute annular urticaria, is common among children. Toddlers and young children are more frequently affected, but the eruption may be seen in teenagers. The most common triggers in children are infections, but antibiotics and vaccinations also have been implicated. Patients can have fever for 1 to 3 days, but do not necessarily have other symptoms of infection. Children may be irritable and uncomfortable but do not appear toxic.
Carrie C. Coughlin
Lesions of urticaria multiforme appear as nummular, annular, arcuate, and polycyclic, erythematous, edematous papules and plaques (Figure 1). The center of the lesions may be dusky or skin colored. Individual lesions last less than 24 hours and may last only minutes to hours. Edema of the hands and feet, as well as face, can be present (Figure 2). In patients with diffuse involvement, it can be difficult for parents to say how quickly lesions resolve, as patients may be nearly covered with flat, resolving patches and newer edematous plaques. As lesions resolve, they may leave a bruise-like appearance that can persist for a few days after the urticaria has resolved (Figure 2).
Many people confuse urticaria multiforme for erythema multiforme, which is generally triggered by a herpes simplex virus infection. Hands and feet are classically involved in erythema multiforme; mucous membranes, especially the lips/mouth, are often involved as well. Erythema multiforme lesions are shaped like a target or iris (central duskiness, rim of sparing, then peripheral erythema). The central portion can be bullous. These lesions are fixed.
Marissa J. Perman
Urticaria multiforme also can be mistaken for serum sickness. However, this reaction is rare now, since few medications contain animal serum. True serum sickness involves other organs in addition to the skin, including blood vessels (vasculitis), kidneys (nephritis), musculoskeletal system (arthralgias and myalgias), and lymph nodes (lymphadenopathy). The primary medication implicated in serum sickness today is antithymocyte globulin, which is derived from horse or rabbit antibodies. This product is used in organ transplant patients and to treat patients with aplastic anemia.
More commonly, urticaria multiforme might be erroneously diagnosed as serum-sickness like reaction (SSLR). The two entities are on a spectrum, as both are considered hypersensitivity reactions, both involve annular red plaques that can have dusky centers, and both commonly have associated hand/feet swelling. Arthralgias can be present with SSLR, and though edema can make walking uncomfortable, urticaria multiforme patients do not typically have joint pain. Lymphadenopathy can also be present in SSLR. Medications cause SSLR; the archetypal trigger is cefaclor.
The differential diagnosis also includes urticarial vasculitis, Kawasaki disease, juvenile idiopathic arthritis, and Lyme disease, among other more rare conditions. The plaques of urticarial vasculitis are fixed and generally painful rather than pruritic. This entity is thought to be much rarer in young children. Kawasaki disease may present with an urticarial eruption, but the lesions are generally fixed and other classic symptoms consistent with Kawasaki disease should accompany the eruption. Additionally, some patients with true urticaria can have a protracted course (lesions lasting more than 6 weeks are considered chronic, and other causes must be investigated).
Treatment of urticaria multiforme is directed at blocking histamine receptors, and is most effective when both H1 and H2 receptors are blocked. A typical treatment regimen includes initial treatment with cetirizine (H1) and ranitidine (H2) for an average of 2 weeks. If symptoms have resolved, the medications can be tapered and discontinued in 3 to 4 weeks.
For mild cases, treatment with cetirizine monotherapy can be considered. Nonsteroidal anti-inflammatory drugs and aspirin should be avoided in these patients, as they trigger mast cell degranulation and can make patients significantly worse. Thus, for patients with fever, acetaminophen is preferred as long as the patient does not have a contraindication to its use. Patients rarely require prednisone. Dual antihistamine therapy generally results in marked improvement in roughly 48 hours.
Recognition of urticaria multiforme can save patients from unnecessary tests and helps the practitioner provide treatment aimed directly at the pathogenesis. Antihistamines work quickly to improve the rash and provide patients relief from their edema and pruritus.
References:
- Dhanya NB. Indian J Dermatol Venereol Leprol. 2008;74:475-477.
- Shah KN. Pediatrics. 2007;119:1177-1183.
- Starnes L. Pediatr Dermatol. 2011;28:436-438.
For more information:
Carrie C. Coughlin, MD, is a pediatric dermatology fellow at The Children’s Hospital of Philadelphia. She can be reached at coughlincc@email.chop.edu.
Marissa J. Perman, MD, is an attending physician at The Children’s Hospital of Philadelphia.
Disclosure: Coughlin and Perman report no relevant financial disclosures.