MTMR2 and bile duct papillary neoplasm: CMT4B1 is an autosomal recessive IPN due to mutations in the MTMR2 (myotubularin-related 2) gene, encoding for a phosphoinositide -PtdInsP3 and PtdIns(3,5)P2- phosphatase, characterized by early onset severe polyneuropathy [174].