A curious case of a blue finger.

This article describes an unusual presentation of a blue finger in a middle-aged woman with no significant past medical history. The patient was diagnosed with Achenbach syndrome, a rare condition that is generally considered transient and benign. The underlying pathophysiology of this condition is unclear, but may be related to transient subcutaneous ecchymosis, possibly from microtrauma. If the condition recurs, a workup can include laboratory tests for autoimmune diseases such as rheumatoid arthritis. Clinician awareness of this presentation may reduce patient anxiety and unnecessary testing.