What is the cause of this rash on this woman’s arms?

This 50-year-old woman presented for evaluation of asymptomatic but persistent discoloration on her arms of 2 months’ duration. She has seen her primary care physician, who ordered a complete blood cell count, a comprehensive metabolic panel, and an antinuclear antibody test, the results of which were all normal. Her rheumatoid factor was found to be elevated, but she denied any joint pain. The only other relevant finding on physical examination was an asymptomatic area of discoloration on her chin that had appeared without any history of trauma.

What is the cause of this rash on this woman’s arms?

1. Eczema
2. Psoriasis
3. Dermatomyositis
4. Livedo reticularis
5. Erythema ab igne

And what is the cause of this rash on her chin?

1. Vitiligo
2. Pityriasis alba
3. Cutaneous lupus erythematosus
4. Tinea faciei
5. Postinflammatory hypopigmentation

Answer on next page

Answer: Livedo reticularis (arm); cutaneous lupus erythematosus (chin)

 Livedo reticularis refers to a mottled appearance to the skin that has a net-like or mesh-like appearance. The condition results from a disturbance of blood flow to the skin, causing decreased blood flow and subsequent reduced oxygen tension to the skin. Livedo reticularis has many associated conditions, including hypercoagulopathies, autoimmune diseases, infections, and drug reactions, to name a few. This patient had an underlying connective tissue disease, with cutaneous lupus erythematosus on her chin and a positive rheumatoid factor. She was educated on avoiding exacerbating conditions such as cold weather; she also was offered oral antimalarial therapy, which she declined given that the rash was asymptomatic. She will have regular follow-up to monitor for possible systemic progression of disease.

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.