Spot diagnosis: eruptive melanocytic naevi during azathioprine therapy in Crohn's disease.

igure 1 Endoscopic image of the sole showing multiple lightrown to black coloured moles. Long term use of thiopurines in the treatment of inflammatory bowel disease (IBD) is associated with the development of non-melanoma skin cancer. Here we present a patient who developed unusual skin abnormalities during azathioprine administration. A 22-year-old woman with known Crohn's disease (located at her ileum en colon) since 2003 was presented at our outpatient endoscopy unit for a routine surveillance colonoscopy. She had been treated with maintenance therapy azathioprine (100 mg per day) for the last 7 consecutive years and had been in clinical remission ever since. During endoscopy, we accidentally noticed multiple, light-brown to black pigmented, smooth-surfaced moles of about 2 mm in diameter on both soles (Fig. 1). Further anamnestic assessment revealed that these moles had developed after initiation of immunosuppressive therapy with azathioprine, and that the moles gradually increased in number, but not in size. After dermatological assessment, the diagnosis of eruptive melanocytic naevi secondary to the use of azathioprine was established. Because of the typical aspect of the lesions and the absence of any signs of malignant transformation, no biopsy specimens were obtained. Eruptive melanocytic naevi, which typically develop on hand palms and soles, are a relatively unknown adverse effect of (longstanding) immunosuppressive therapy. The nature of these naevi remains unclear, but regular screening for dysplastic naevi or melanoma seems indicated, keeping in mind the potential risk of malignant transformation.1 Whether or not surveillance colonoscopy in patients with inflammatory bowel disease should include inspection of the soles remains unclear.