However, PGL4 is more likely to be associated with TAPGL and/or PC, is more likely to present with symptoms from local tumour mass, and malignant disease occurs in around a third of patients (Benn et al. 2003, Gimenez-Roqueplo et al. 2003, Brouwers et al. 2006, Amar et al. 2007, Timmers et al. 2007). This evidence concerns the gene SDHB and pachyonychia congenita.