More recently, in collaboration with Dr. Luis Caraballo and Dr. Nathaly Acevedo (Instituto de Investigaciones Inmunológicas, Universidad de Cartagena, Cartagena, Columbia), we observed an increased frequency of the C allele of leukotriene C4 synthase (LTC4S), the enzyme responsible for the synthesis of leukotrienes, in cross-reactive NSAID hypersensitive patients with urticaria and/or angioedema. Here, LTC4S is linked to angioedema.