A 76-year-old immunocompetent white woman with coronary artery disease and severe mitral valve regurgitation was admitted to the hospital for 3-vessel coronary artery bypass grafting and mitral valve replacement. On postoperative day 1, an approximately 2-cm oval, pink, asymptomatic patch developed in the left lateral inguinal crease. This lesion was relatively stable for 6 days and then rapidly progressed into a 2.5 × 2.0-cm rimmed erythematous plaque with ulceration and central caseation (Figure 1). This ulcer was mildly tender to palpation and anesthetic to prick testing. The patient denied any trauma, pressure, or surgical procedures to this region. Differential diagnoses included bacterial infection, deep fungal infection, mycobacterial infection, and radiation dermatitis.
Whalen JG, Mully TW, English JC. Spontaneous Citrobacter freundii Infection in an Immunocompetent Patient. Arch Dermatol. 2007;143(1):115-126. doi:10.1001/archderm.143.1.124