HLA-B*58:01 Genotyping to Prevent Cases of DRESS and SJS/TEN in East Asians Treated with Allopurinol-A Canadian Missed Opportunity [Formula: see text].

BACKGROUND AND OBJECTIVE: East Asians exposed to the urate-lowering drug allopurinol have a predilection for severe cutaneous drug reactions such as drug-induced hypersensitivity syndrome or drug reaction with eosinophilia and systemic symptoms (DRESS) and Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). Screening is recommended in patients of East Asian descent for the presence of HLA-B*58:01 prior to allopurinol initiation to avoid these complications. Utilization rates of the HLA-B*58:01 predictive screening test within the Greater Vancouver area, which has a population composed of 40.1% people of East Asian descent, are unknown. MEASURES: We identified cases of DRESS or SJS/TEN due to allopurinol using the Vancouver General Hospital dermatology consult service database. We next compared the frequency in which the HLA-B*58:01 screening test was ordered since 2012 to the estimated frequency of new prescriptions for allopurinol prescribed for the management of gout among the East Asians. RESULTS: We report 5 cases of East Asian patients exposed to allopurinol for management of gout between 2012 and 2016, who developed DRESS (4 patients) or SJS/TEN (1 patient). All were of HLA-B*58:01 genotype, representing preventable cases. The HLA-B*58:01 test was ordered 6 times in 2012, whereas the estimated number of new cases of allopurinol-prescribed gout among patients of East Asian descent during that time period was 13. For 2012, testing was ordered for only 46% of at-risk patients. CONCLUSION: We continue to observe cases of severe cutaneous drug reactions among high-risk individuals due to allopurinol exposure. The HLA-B*58:01 screening test for allopurinol hypersensitivity is underutilized in our geographic area.

Amelanotic Lentigo Maligna Melanoma: Mohs Surgery as the Definitive Treatment of an Invisible Tumour.

Amelanotic lentigo maligna melanoma represents <2% of melanomas. Diagnosis is delayed owing to the lack of lesion pigmentation and advanced disease at presentation. Excision with appropriate margins is the treatment standard, but the starting point for such margins is often unclear. We describe 2 patients with amelanotic melanoma treated by Mohs micrographic surgery (MMS) that would not have been cleared by wide local excision alone and provide an extensive review of the literature. Both patients presented with histologic diagnoses of malignant melanoma, one with a barely perceptible biopsy site scar on the left infraorbital cheek/lower eyelid (Breslow 1.8 mm) and the second with an amelanotic tumour on the right helix (Breslow 10 mm). Due to location, aggressive histology, amelanotic appearance, and no apparent surrounding skin surface changes, MMS was elected to maximise margin control. For patient 1, invasive and in situ tumour was found at the American Joint Committee on Cancer-recommended margin of 1.5 cm, and the final defect measured 8.5 × 4.8 cm. Patient 2 had a significant invasive and amelanotic lentigo maligna component, resulting in a 9.0 × 6.5-cm defect. MMS allows for immediate histologic feedback on tumour margins of a clinically invisible tumour and thus offers the most definitive treatment.