April 09, 2016
3 min read

A 13-year-old boy presents with red, annular rash on torso, thighs

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A 13-year-old boy without significant past medical history presented to the outpatient dermatology clinic for evaluation of a rash. The patient reported development of a red, annular rash on his chest 2 weeks ago that increased in size rapidly. Over the previous few days, similar lesions developed on his abdomen, back and thighs, yet he denied pruritus or pain. The patient tried oral diphenhydramine and a topical steroid cream without improvement of the rash.

The patient also noted recent development of mild left-sided jaw and neck pain over the past 4 days. He reported feeling more fatigued over the past week. He denied any other joint pain, myalgias or arthralgias, and reported no occurrences of fever, chills, night sweats, photophobia, headache or sore throat.

On exam, he had multiple, large, annular red patches — many greater than 10 cm — on his chest, abdomen, back and proximal upper extremities. Babinski sign was absent bilaterally. Neck stiffness was noted on exam, but no frank meningismus was appreciated.

Figure 1. Expanding annular erythematous patches with central clearing of the back (left)
and abdomen (right).

Source: Images courtesy of Streicher, JL.

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Case Discussion:

Erythema migrans (C) is an annular rash that represents one of the earliest signs of Lyme disease. The annular rash is characterized by erythematous expanding patches with advancing borders and central clearing with a diameter of at least 5 cm. Lyme disease is caused by the tick-borne spirochete, Borrelia burgdorferi, which is transmitted by the Ixodes genus of ticks. In the United States, it is primarily transmitted by Ixodes scapularis, commonly known as the deer tick or blacklegged tick, and is most frequently observed in the Northeast and mid-Atlantic region. The transmission risk is low if the tick is removed within the first 24 hours of attachment. The clinical findings of Lyme disease are divided into early — including early localized and early disseminated — and late stages.

Jenna L. Streicher

In early involvement, erythema migrans (EM) represents infection that is usually restricted to the skin. Even without treatment, the rash will eventually clear spontaneously over several weeks. Once the organism disseminates, individuals can develop multiple lesions of EM as seen in this patient. In this stage, systemic symptoms are common including neurologic manifestations, such as facial palsy, meningitis and migratory arthralgias. Late disease is much less common due to recognition of early findings. Untreated cases of late Lyme disease are characterized by arthritis and neurologic disease.

The differential diagnosis includes tinea corporis, erythema marginatum, and erythema annulare centrifugum (EAC). Despite being annular, tinea corporis is scaly with central clearing that evolves more slowly. Erythema marginatum is an annular erythema that is seen with acute rheumatic fever. It is characterized by pink polycyclic rings that spread rapidly and recur in crops. The skin lesions are most commonly found on the trunk and proximal extremities. A recent group A streptococcal disease is part of the diagnostic criteria for rheumatic fever.

Marissa J. Perman

EAC also should be included in the differential of annular erythema in a child. It is characterized by erythematous annular lesions that slowly enlarge and often have a fine collarette of scale on the trailing edge of the erythema. The etiology of EAC is unknown; however, it is thought to represent a hypersensitivity reaction to a multitude of entities including fungi, viruses and drugs.

The suspicion for Lyme disease in this patient was high due to the characteristic skin findings as well as pertinent history of a recent stay at a summer camp with many days spent hiking in the woods. He was found to have elevated IgM and IgG Lyme antibodies on ELISA, in addition to a positive Lyme Western blot for IgM and IgG. He was successfully treated with oral doxycycline 100 mg two times per day for 21 days in the setting of early disseminated disease with resolution of his cutaneous and systemic symptoms.

EM represents an early manifestation of Lyme disease and is characterized by enlarging erythematous annular patches with central clearing. Practitioners should be aware of the cutaneous findings as early recognition of Lyme disease with initiation of appropriate antibiotic therapy can prevent the late manifestations of the disease.

Disclosures: Streicher and Perman report no relevant financial disclosures.