Viral Exanthem and Fever

April 1, 2005

THE CASE: A 3-year-old boy is brought to the office by his mother. The previous evening, she had noticed a single large red spot on the back of his thigh. This morning, his whole body was covered with a similar rash, and he had a temperature of 38.8°C (102°F). The mother administered 1 dose of acetaminophen at home for the fever; the rash was asymptomatic.

THE CASE: A 3-year-old boy is brought to the office by his mother. The previous evening, she had noticed a single large red spot on the back of his thigh. This morning, his whole body was covered with a similar rash, and he had a temperature of 38.8°C (102°F). The mother administered 1 dose of acetaminophen at home for the fever; the rash was asymptomatic.

During the previous week, the child experienced vomiting, diarrhea, and abdominal pain of several hours' duration. There is no history of trauma, recent travel, tick bites, contact with sick persons, headache, cough, rhinorrhea, stiff neck, sore throat, or joint swelling. The child is not taking any medications or herbal remedies. He was born prematurely at 34 weeks and has a history of atopic dermatitis.

On examination, the child is afebrile, alert, and active, and displays age-appropriate behavior. The rash consists of generalized symmetric large target lesions with erythematous raised borders and nonscaly pale centers on the trunk, buttocks, extremities, and face. The examination is unremarkable except for the rash.

Which of the following conditions in the differential do you suspect?

• Henoch-Schönlein purpura (HSP)

• Erythema multiforme minor

• Erythema migrans

• Viral exanthem

DISCUSSION: The child was admitted to the hospital for further observation and evaluation. Results of a complete blood cell count with differential, a basic metabolic panel, and urinalysis were normal. Mycoplasma titers, blood cultures, and a direct fluorescent antibody nasal swab for respiratory viruses all had negative results. A diagnosis of viral exanthem was made. The child continued to be afebrile and the rash faded markedly the next day.

Viral exanthems caused by enteroviruses may occur throughout the year; the incidence peaks during the late summer and fall. The cutaneous eruption may appear as a morbilliform, vesicular, petechial, or urticarial rash with target lesions; it is usually associated with fever. Infections caused by cytomegalovirus, Epstein-Barr virus, and respiratory viruses may be associated with macular, morbilliform, or urticarial exanthems, which sometimes are difficult to differentiate from drug rashes. Target lesions that are intensely pruritic suggest urticaria. The diagnosis of a viral exanthem is made by exclusion, as it was in this case. Treatment is not given unless a bacterial cause is suspected, in which case empiric therapy is prescribed until the diagnosis is established.

HSP was suspected initially because the child had a recent history of diarrhea and abdominal pain followed several days later by the rash on his lower extremities.HSP, a vasculitis of small vessels, is the most common cause of nonthrombocytopenic purpura in children. The rash can initially resemble target lesions, but typically it begins as pink maculopapules that progress to petechiae or palpable purpura. The lesions evolve from red to purple to rusty brown before eventually fading. Several organ systems may be involved during the acute phase of the disease, resulting in arthritis, renal and GI manifestations, edema in dependent areas, and occasionally hepatosplenomegaly and lymphadenopathy. CNS involvement occurs rarely but may result in serious complications. Because there are no diagnostic laboratory tests for HSP, a thorough history and physical examination are essential.

Erythema multiforme minor is a distinctive acute hypersensitivity syndrome that may be caused by a number of viruses, as well as by medications, bacterial infections, foods, and immunizations. It may also arise in association with connective tissue disorders. Medications and infectious diseases are the most common triggers in children. A symmetric rash usually appears on the dorsa of the hands and feet and extensor surfaces of the arms and legs. The palms and soles are commonly affected. The initial lesions are dusky red macules or papules that evolve into target lesions with multiple concentric rings of color change. In most children, mucous membrane involvement is minimal or absent. The disease is self-limited. Systemic manifestations are limited to low-grade fever, malaise, and myalgia. Treatment consists of symptomatic support and reassurance.

Erythema migrans marks the onset of Lyme disease, the most common tick-borne illness in the United States. Lyme disease is caused by the spirochete Borrelia burgdorferi, which is transmitted to humans through the bite of an infected tick of the Ixodes species. Most cases occur in southern New England, the eastern Middle Atlantic states, and the upper Midwest. The onset of illness, which corresponds to the life cycle of the tick, usually occurs between May and October. Most cases present in June and July.

A single papule erupts 3 to 30 days after a tick bite and expands quickly to form an enlarging annular red plaque with central clearing. The secondary lesions, which may develop several days later, are usually smaller than the primary lesion and are commonly accompanied by fever, myalgia, headache, malaise, conjunctivitis, and lymphadenopathy. Other manifestations may include aseptic meningitis, uveitis, or carditis. Paralysis of the facial (seventh) cranial nerve, which is more common in children, is usually idiopathic; however, it may be a presenting sign of Lyme disease.

Arthritis, the hallmark of late disease, tends to involve large joints; the knee is affected in 90% of cases. CNS involvement in children is rare. The diagnosis can be made clinically in the early stages of the disease based on the presence of erythema migrans. Serologic testing is the standard of diagnosis in later stages. However, serologic testing is not recommended for children with nonspecific symptoms and those with no history of exposure or for children in areas where Lyme disease is not endemic. Antibiotic therapy is required at all stages of Lyme disease.

References:

FOR MORE INFORMATION:

Behrman RE, Kliegman R, Jenson HB, eds. Nelson Textbook of Pediatrics. Philadelphia: WB Saunders Co; 2000:728-729, 911-912, 1989-1990.

Cohen BA. Atlas of Pediatric Dermatology. London and St Louis: Wolfe; 2000: 105-106, 154, 156-160, 165-166, 171-172.

Zitelli BJ, Davis HW. Atlas of Pediatric Physical Diagnosis. Philadelphia: Lippincott; 1992:191-192, 203-204, 232-233.