Department of Medical Genetics, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan. Department of Child Health and Pediatrics, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan. Department of Medical Genetics, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan; Division of Otorhinolaryngology - Head & Neck Surgery, Department of Sensory and Locomotor Medicine, Faculty of Medical Science, University of Fukui, Fukui, Japan. Division of Otorhinolaryngology - Head & Neck Surgery, Department of Sensory and Locomotor Medicine, Faculty of Medical Science, University of Fukui, Fukui, Japan. Department of Medical Genetics, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan. Electronic address: enoguchi@md.tsukuba.ac.jp.