A Blue-Gray Subungual Discoloration—Quiz Case

A 29-year-old woman presented with a 4-month history of a large, approximately 20 8-cm blue patch on her left forearm that had appeared overnight (Figure 1). She told us that she had noticed the blue patch after she had driven “nonstop” from Amsterdam, the Netherlands, to Spain in a state of rage after a fight with her partner. She had a several-year history of diabetes mellitus, for which she injected insulin. She used no other medications. A dissociative disorder had previously been diagnosed by a psychiatrist. Examination of the left forearmshowed striking clear-blue dyschromia of the skin, without induration or any sign of trauma. A skin biopsy was performed (Figure 2). What is your diagnosis?