Case Report

Low-grade fever, erythematous rash in pregnant woman • Dx?

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► Low-grade fever
► Erythematous rash




A 31-year-old woman presented to her obstetrician’s office at 16 weeks’ gestation with a 2-day history of low-grade fever and an erythematous rash measuring 1 x 4 cm on her right groin. She had a medical history of a penicillin allergy (urticaria) and her outdoor activities included gardening and picnicking.

We suspected that she was experiencing an allergic reaction and recommended an antihistamine (diphenhydramine). The patient returned 4 days later with new symptoms including headache, photophobia, neck pain, unilateral large joint pain, and periorbital cellulitis, as well as expansion of her rash. She was afebrile and an examination revealed that the 1 x 4 cm rash on her groin had grown; it was now a demarcated erythematous rash with faint central clearing measuring 5 x 8 cm. Right periorbital erythema and nuchal rigidity were also noted.

Because of her expanding rash and nuchal rigidity, we suspected Lyme meningitis and we referred her to the emergency department. Within 24 hours, the rash had spread to her abdomen, thigh, and wrist, and was consistent with erythema migrans.

Laboratory evaluation revealed an increased number of white bloods cells (13.5 million cells/mcL; normal range 4.5-11.0 million cells/mcL), and an increased number of neutrophils (10.8 million cells/mcL; normal range 1.8-8 million cells/mcL), indicating leukocytosis with a left shift. Lab tests also revealed a low hemoglobin level (10.6 g/dL; normal range 12-16 g/dL) and a mean corpuscular volume of 85.6 fL/red cell (normal range 80-100 fL/red cell), indicating microcytic anemia. A lumbar puncture was negative for disseminated Lyme disease by Gram stain, culture, and polymerase chain reaction.


A diagnosis of Lyme disease was confirmed with a positive Lyme titer serology via an enzyme-linked immunosorbent assay. The rash and other symptoms responded promptly to intravenous ceftriaxone 2 g, and the patient was discharged home on oral cefuroxime 500 mg bid for 14 days.


Lyme disease is the most common vector-borne illness in the United States, concentrated heavily in the Northeast and upper Midwest.1 The most recent information released by the Centers for Disease Control and Prevention (CDC) lists Vermont, Maine, Pennsylvania, Rhode Island, Connecticut, New Jersey, Massachusetts, Delaware, New Hampshire, and Minnesota as the states with the highest incidence of Lyme disease.2

The number of reported cases in the United States has increased over the past 2 decades, from approximately 11,000 in 1995 to about 28,000 in 2015.3 Over the past year, we have seen several cases of Lyme disease in the obstetric population of our own practice.

Prompt treatment is crucial. Pregnant women who are acutely infected with Borrelia burgdorferi (the primary cause of Lyme disease) and do not receive treatment have experienced multiple adverse pregnancy outcomes, including preterm delivery, infants born with rash, and stillbirth.4 Additional concern exists for fetal cardiac anomalies, with data showing that there are twice as many cardiac defects in children born to mothers residing in endemic regions.5

What animal studies have taught us about Lyme disease

The potential causal relationship between Lyme disease and fetal demise was first studied in 2007. This case report involved the stillbirth of a full-term baby from an acutely infected woman who did not receive treatment. She experienced erythema multiforme 6 weeks prior to delivery.6

A fetal echocardiogram is reasonable in pregnant women acutely infected with Lyme disease during the first trimester, given the high potential for fetal cardiac anomalies.

The vast majority of research on Lyme disease in pregnancy comes from work with mice and dogs. These studies confirmed that acute infection with Lyme disease is associated with an increased risk of adverse fetal outcomes, specifically fetal death.7

Silver et al further researched the association using murine models in the 1980s. They found that fetal death occurred in 12% of acutely infected mice, compared with none of the mice that were chronically infected.7

In 2010, Lakos and Solymosi examined the effects of Lyme disease on pregnancy outcomes in acutely infected women. Seven out of 95 pregnant women acutely infected with B burgdorferi experienced fetal demise, further supporting the association seen in animal experiments.8

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