Lyme Disease Rash in a Child: When a Negative Test Delays Diagnosis

A circular rash was mistaken for dermatitis
The Lyme test was negative early
Clinical judgment led to the correct diagnosis—and recovery

A 6-year-old child presented with a circular rash on the left side of her face. It was initially diagnosed as allergic dermatitis and treated with topical steroids—but the rash did not improve, according to Banadyha and colleagues in Pediatric Neonatology.

Over the next 6 weeks, the rash spread to the back of her head. She developed systemic symptoms, including malaise and a low-grade fever of 37.7 ºC. An initial enzyme-linked immunosorbent assay (ELISA) test for Lyme disease was negative.

When Lyme Disease Tests Are Negative Early

There was no history of a tick bite and no joint or neurologic complaints. Still, clinicians suspected Lyme disease because the child lived in an endemic region.

This case highlights a common clinical challenge: Lyme disease tests may be negative early in infection, particularly before antibodies are detectable—a limitation discussed in our Lyme test accuracy guide.

Why the Rash Matters

A circular, expanding rash is one of the most recognizable early signs of Lyme disease, though it is often mistaken for other conditions. These patterns are outlined in our Lyme disease symptoms guide.

In children, early symptoms may be subtle or misinterpreted, which can delay diagnosis and treatment.

Treatment Based on Clinical Judgment

Based on clinical suspicion, the child was treated with oral cefuroxime, consistent with the International Lyme and Associated Diseases Society (ILADS) guidelines.

Two weeks after starting antibiotics, Lyme disease was confirmed with a positive IgG Western blot test.

The outcome was favorable. “The girl remained asymptomatic even after a 1.5-year follow-up,” the authors reported.

Key Lessons from This Case

• Erythema migrans may appear before antibodies are detectable, leading to false-negative early tests
• Lyme disease can be diagnosed clinically in patients with a characteristic rash in endemic areas
• A known tick bite is not required to make the diagnosis

Why This Matters

Misdiagnosis of Lyme disease—especially in children—can delay appropriate treatment. Cases like this reflect broader patterns seen in delayed Lyme disease diagnosis, where early signs are missed or attributed to more common conditions.

When clinical signs point to Lyme disease, treatment should not be delayed while waiting for laboratory confirmation.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention