Protein‐truncating variants (PTVs) in BAP1 dramatically increase the risk for both UM and CM (Abdel‐Rahman et al. 2011), as part of the BAP1 tumour predisposition syndrome (Walpole et al. 2018) and variants in POT1 and CDKN2A predispose to CM (Robles‐Espinoza et al. 2014), while case reports have suggested that POT1 and CDKN2A are risk genes for UM (Hearle et al. 2003; Kannengiesser et al. 2003; Nathan et al. 2021), although with limited penetrance (Abdel‐Rahman et al. 2020). This evidence concerns the gene CDKN2A and cutaneous mastocytosis.