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JAMA Clinical Challenge

A Solitary Red Patch

Image of Shin with 3-cm macular lesion

Sarah Y. Lee, BA
Lisa Shen, MD
Emily L. Keimig, MD

A 25-year-old woman with type 2 diabetes mellitus comes to the emergency department for evaluation of a hyperpigmented lesion on the shin. The lesion appeared as a small reddish-brown macule 3 years ago and has gradually increased in size. During the past several months, the lesion has become indented and increasingly tender. Cutaneous examination reveals a 3-cm sclerotic reddish brown patch with central yellow deposits (Figure). Laboratory evaluation includes a random blood glucose level of 217 mg/dL (12 mmol/L). The patient denies systemic symptoms, including fevers and chills, and is primarily concerned about the changing appearance of the lesion and the new-onset tenderness.

See the full article for an explanation and discussion.

Author Affiliations: Drs Keimig (emily.keimig@northwestern.edu) and Shen and Ms Lee are affiliated with the Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, Illinois.