Intended for healthcare professionals

Endgames Case Review

A cutaneous presentation of a common condition

BMJ 2015; 351 doi: (Published 17 December 2015) Cite this as: BMJ 2015;351:h6711
  1. Adam Daunton, core medical trainee1,
  2. Gerald Langman, consultant histopathologist2,
  3. J M R Goulding, consultant dermatologist2
  1. 1Queen Elizabeth Hospital, University Hospitals Birmingham NHS Foundation Trust, Birmingham B15 2GW, UK
  2. 2Solihull Hospital, Heart of England NHS Foundation Trust
  1. Correspondence to: A Daunton adamdaunton{at}

A 25 year old woman was reviewed on the ward by the dermatology team for persistent, painful intertriginous skin erosions beneath both breasts and in both groins. She had been admitted over a month ago with cellulitis around the erosions, which initially responded to intravenous antibiotics but needed several repeat courses owing to recurrence.

Crohn’s disease had necessitated a total colectomy at age 18 years. She also had severe learning difficulties and behavioural problems.

She could not tolerate topical treatments. The only regular drugs at admission were mesalazine 1500 mg daily and clozapine. High dose oral corticosteroids before colectomy caused a marked transient psychosis and she had not received further systemic corticosteroids since.

She was obese with deep sloughy linear erosions demonstrating the “knife-cut” sign beneath the abdominal apron, in the inguinal creases, and under both breasts (fig 1). She also had an eroded ulcer in her right labium majus.

Fig 1 Knife-cut ulcer in the right submammary fold

Multiple skin swabs were negative for bacterial, candidal, and herpes simplex virus (HSV) infections. Initial skin biopsy showed only non-specific scarring in the dermis, but a deeper one showed non-caseating granulomatous inflammation.


  • 1. Which differential diagnoses must be excluded in this patient?

  • 2. What investigations are needed to reach a diagnosis?

  • 3. How should this condition be managed?

  • 4. What other cutaneous manifestations can occur in this condition?


1. Which differential diagnoses must be excluded in this patient?

Short answer

Linear erosive HSV infection, cutaneous Crohn’s disease, bacterial and fungal infections.


The term “knife-cut” sign was originally used to refer to the linear fissures commonly seen on colonoscopy in patients with Crohn’s disease. It was later used to describe the cutaneous linear erosive lesions seen in some patients with Crohn’s disease affecting the skin (termed metastatic Crohn’s disease).1 However, other disorders may also produce linear erosive fissures with a similar appearance. …

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