ERG and pachyonychia congenita: Among the top 20 most significantly upregulated transcripts in CAN versus AN samples, 45% were genes which have previously been studied in relation to PC biology and/or progression of PC (PC-associated genes) (Table S7), e.g. ERG and AMACR. The top 20 most significantly differentially downregulated transcripts in CAN versus AN samples, comprised 65% PC-associated genes, e.g. the keratin KRT5 and Tumour Protein TP63. To identify classes of genes that were over or under-represented between sample types, GSEA was performed between the CAN and AN.