Leg rashes and unwell – 10 cases

Erythema chronicum migrans

Erythema migrans is due to Lyme borreliosis in more than 90% of cases.

Erythema migrans is an erythematous, expanding annular plaque with a bull's eye appearance, which typically appears a few days after an infected tick bite. Other symptoms may include fever, arthralgia, headache and myalgia. The diagnosis is made clinically as serology may take several weeks to obtain and is negative in 60%, as in this patient.

Lyme disease is due to spirochaetes, Borrelia burgdorferi, B. garinii and B. afzelii transmitted via Ixodes ticks. It is a multisystem infection and may result in disease of the eyes, heart, joints, nervous system and genitourinary system. Borrelia may also give rise to lymphocytoma cutis and acrodermatitis chronic atrophicans. All its manifestations are rarely seen in New Zealand, as endemic ticks do not carry the causative spirochaetes.