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Five atypical exanthems call for reassurance.

While most exanthems are self-limiting, some are not, making it important to establish a specific diagnosis, according to Dr. Anthony J. Mancini.

"Parents want to go read up on these things, and they want to know how long it's going to take to go away," Dr. Mancini said in an interview. "If you can characterize it ... it's helpful for parents to know. At least they may have some answers. They know that it's going to take a while to resolve, and that saves you from follow-up phone calls and visits to the office when they're frantic because it's still there 4 weeks later."

Clinicians have learned to keep an eye out for the truly bad actors, like oral mucosa necrosis that could signal Stevens-Johnson syndrome, or the centripetal spread of exanthem with petechiae from a tick bite that could signal Rocky Mountain spotted fever.

At the women's and pediatric dermatology seminar in San Francisco, sponsored by Skin Disease Education Foundation (SDEF), Dr. Mancini reviewed common exanthems, and many that aren't so common, paying special attention to five of the newer or atypical exanthems: acute generalized exanthematous pustulosis (AGEP), Arcanobacterium haemolyticum, Gianotti-Crosti syndrome, papular-purPuric gloves and socks syndrome, and unilateral laterothoracic exanthem.

Acute Generalized Exanthematous Pustulosis

AGEP is often mistaken for drug-induced pustular psoriasis, and the literature is filled with a wide range of reported drug associations, including amoxicillin, erythromycin, NSAIDs, and even pseudoephedrine, but current thinking is that it is often viral, at least in children.

"It's an important entity to recognize, because AGEP can have a sudden onset, with fevers and numerous widespread nonfollicular pustules, which can look a lot like pustular psoriasis," said Dr. Mancini, head of pediatric dermatology at Children's Memorial Hospital in Chicago. It's self-limited, but children do tend to appear more toxic with AGEP than with some of the other exanthems, especially if they are young. They may have low-grade fevers, and their white counts may be mildly elevated. Treatment is Supportive, with antihistamines, cool compresses, and topical steroids if patients are uncomfortable. AGEP will resolve over 2 weeks or so with desquamation.


A. haemolyticum

Often masquerading as scarlet fever, Arcanobacterium haemolyticum typically appears in adolescents and young adults as a sore throat with a scarlet fever-like rash. It is important for physicians to recognize and diagnose A. haemolyticum because it can be treated, noted Dr. Mancini.

The first clue that it is not scarlet fever or mononucleosis is a negative throat culture for strep and a negative Monospot. Most labs can test for A. haemolyticum, but only if they know to look, because they need to plate it on a different agar.

Although A. haemolyticum will probably resolve on its own with time, children can be treated effectively with a macrolide antibiotic such as an erythromycin, azithromycin, or clarithromycin. Patients do not respond well to penicillin antibiotics, an important distinction from streptococcal infection, he said.

Gianotti-Crosti Syndrome

Physicians have probably not diagnosed this syndrome because they have not looked closely at distribution. "This exanthem likes to involve the outer arms, the outer legs, the buttocks, and the face. And it almost always spares the trunk, or at least the trunk will be much less involved than everywhere else," he said.

Physicians need to remember that, while they may have learned in residency that Gianotti-Crosti syndrome is associated with hepatitis B, that's rarely true in the United States. It is usually caused by the Epstein-Barr virus and requires no treatment. It will resolve, but it may take up to 2 months.

Papular-Purpuric Gloves and Socks Syndrome

Caused most often by parvovirus B19, this syndrome is named for the characteristic rash appearing on a child's palms and soles, with sharp cutoffs at the wrist and ankle, according to Dr. Mancini.

The virus is self-limited and typically requires only symptomatic treatment, but it is important to establish a diagnosis because parvovirus B19 can cause fetal infections in utero and lead to a variety of complications. Parvovirus B19 also causes Fifth disease, but there is an important difference, he pointed out. The "slapped cheeks" of Fifth disease are thought to appear only after the child is no longer viremic. A child with papular-purpuric glove and socks syndrome may still be viremic when there is a rash, however, and so should be kept away from pregnant women who are early in gestation.

Unilateral Laterothoracic Exanthem

Most physicians "have probably seen unilateral laterothoracic exanthem, but they may have misdiagnosed it as contact dermatitis," Dr. Mancini said. Beginning on one side of the body, usually at the arm, armpit, or trunk, the exanthem may initially look like a contact dermatitis but then begins to spread. Even after spreading, the exanthem maintains predominance on the initial side of involvement.

The cause is unknown, but it is probably viral, he said. It requires no treatment and typically takes 6-8 weeks to resolve.

Dr. Mancini disclosed being a consultant to SkinMedica and Galderma, and on the speakers bureau of Promius and Galderma. SDEF and this news organization are owned by Elsevier.
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Title Annotation:CLINICAL ROUNDS
Author:Finn, Robert
Publication:Pediatric News
Geographic Code:1USA
Date:Nov 1, 2009
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