PMP22 and bile duct papillary neoplasm: The most common IPN subtype, CMT1A is caused by a 1.5‐Mb tandem duplication of chromosome 17p11.2 (Lupski et al., 1991) which results in trisomy of the gene encoding peripheral myelin protein 22 (PMP22, OMIM:*106907) (Lupski et al., 1992; Patel et al., 1992; Timmerman et al., 1992; Valentijn et al., 1992).