Myotonic Dystrophy Type 1 (DM1) in combination with demyelinating neuropathy is very rare in literature. In this Study, DM1 and demyelinating neuropathy were demonstrated clinically and electromyographically in a 43-year-old female patient from Turkey. In the patient an expanded CTG repeat in the Myotonic Dystrophy Protein Kinase (DMPK) gene was confirmed in combination with a duplication in the Charcot-Marie-Tooth Disease (CMT1A) gene. DM1 was also determined in her 25-year-old son. (C) 2009 Elsevier B.V. All rights reserved.