title: The "Knife-Cut Sign" Revisited: A Distinctive Presentation of Linear Erosive Herpes Simplex Virus Infection in Immunocompromised Patients.
abstract: BACKGROUND
  The "knife-cut sign" is a distinctive presentation of linear erosive herpes simplex virus infection in immunocompromised patients.
  
  
  OBJECTIVE
  To describe a man whose herpes simplex virus infection-related skin lesions demonstrated the "knife-cut sign" and to review the characteristics of reported immunosuppressed individuals with "knife-cut" cutaneous herpes simplex virus lesions.
  
  
  METHODS
  A man with multiple myeloma and post-stem cell transplant cutaneous graft-versus-host disease managed with systemic prednisone and sirolimus developed disseminated cutaneous herpes simplex virus infection with virus-associated linear ulcers of the inguinal folds and the area between his ear and scalp; the lesions at both sites had a distinctive "knife-cut" appearance. Using the PubMed database, an extensive literature search was performed on herpes simplex virus, immunocompromised patient, and "knife-cut sign".
  
  
  RESULTS
  Herpes simplex virus infection-associated skin lesions that demonstrate the "knife-cut sign" present in patients who are immunosuppressed secondary to either an underlying medical condition or a systemic therapy or both. The distinctive virus-related cutaneous lesions appear as linear ulcers and fissures in intertriginous areas, such as the folds in the inguinal area, the vulva, and the abdomen; in addition, other sites include beneath the breast, within the gluteal cleft, and the area between the ear and the scalp. Not only herpes simplex virus-2, but also herpes simplex virus-1 has been observed as the causative viral serotype; indeed, herpes simplex virus-1 has been associated with genital and inframammary lesions in addition to those above the neck. Direct fluorescent antibody testing is a rapid method for confirming the clinically suspected viral infection; however, since false-negative direct fluorescent antibody testing occurred in some of the patients, it may be prudent to also perform viral cultures and possibly lesional skin biopsies to establish the diagnosis. The herpes simplex virus infection-related skin lesions clinically improve once systemic antiviral therapy is initiated.
  
  
  CONCLUSIONS
  In immunosuppressed individuals, the "knife-cut sign" is a distinctive presentation of cutaneous linear erosive herpes simplex virus infection. Recognition of the linear ulcers in intertriginous areas and body folds should prompt the clinician to consider herpes simplex virus infection-associated skin lesions in an immunocompromised patient and to initiate systemic antiviral treatment while awaiting the results of laboratory evaluation to confirm the suspected diagnosis.
authors.affiliation: Department of Dermatology, University of California San Diego, San Diego, California.
authors.forename: Philip R
authors.initials: PR
authors.lastname: Cohen