A 58-year-old woman was seen for a progressively enlarging erythematous lesion that had arisen on her cheek 7 days earlier. There were no associated symptoms. She had received topical antifungal treatment with no improvement, and she did not recall any trauma or insect bite. Physical examination revealed an annular erythematous plaque on the patient's right cheek, with an elevated border and partial central clearing, with no flaking, hemorrhage, or necrosis (Fig. 1). On a diagnostic suspicion of erythema chronicum migrans, we requested complete blood count and biochemistry, which were normal, and serology for Borrelia IgM antibodies, which was positive; serology performed 3 weeks later showed the development of Borrelia IgG antibodies. Culture for fungi and bacteria was negative. Doxycycline, 100mg/12h, was administered for 3 weeks, achieving complete resolution. Lyme disease is caused by the spirochete Borrelia burgdorferi transmitted by the bite of ticks of the genus Ixodes. The initial stage of the disease presents with an influenza-like illness and typical skin manifestations, with erythema chronicum migrans, characterized by progressive spread with central clearing. Untreated, the clinical course of Lyme disease is similar to that of syphilis, with an early localized stage, an early disseminated stage, and a late persistent final stage. Early antibiotic treatment can prevent progression to subsequent phases, which are associated with more severe organ involvement.

Figure 1

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