What is the cause of this woman’s rash?
This 62-year-old woman presented with a 1-month history of a slightly itchy, sparse rash on her trunk that had persisted. She was concerned given that she had breast cancer 1 year ago, which had been treated with lumpectomy and radiation therapy. The results of her most recent follow-up examination, including mammography, had shown no recurrence.
What is the cause of this woman’s rash?
- Tinea corporis
- Pityriasis rosea
- Erythema annulare centrifugum
- Nummular eczema
- Metastatic breast cancer
Answer on next page.
Answer: Erythema annulare centrifugum
To allay the concerns of the patient and to establish the diagnosis, a skin biopsy was performed, the results of which revealed changes consistent with erythema annulare centrifugum (EAC). The patient was prescribed a topical corticosteroid cream, which resolved the lesions, but she was told that the rash could return.
EAC is a reactive process of uncertain etiology in most cases. While malignancy has been a reported association of the condition, it is very rare, and the results of her recent workup should be reassuring. Underlying infection, drug reactions, or even insect or tick bites have thought to be most commonly responsible for producing the characteristic gyrate pattern of EAC lesions with trailing scale.
Tinea corporis would be a reasonable thought here, given the annular lesions, while pityriasis rosea would also feature oval-shaped macules. Nummular eczema tends to be more common on the extremities and to be seen in the background of atopy and/or dry skin. Cutaneous metastatic breast cancer lesions would typically not be scaly and would be more indurated than the lesions seen here.
David L. Kaplan, MD, is a clinical assistant professor of dermatology at the University of Missouri–Kansas City School of Medicine in Kansas City, Missouri, and at the University of Kansas School of Medicine in Kansas City, Kansas. He practices adult and pediatric dermatology in Overland Park, Kansas.