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Published on: April 4, 2018
Clinical spectrum of POLR3-related leukodystrophy caused by biallelic POLR1C pathogenic variants
Laurence Gauquelin1, Ferdy K Cayami1, László Sztriha1
1Department of Neurology and Neurosurgery (L.G., L.T.T., K.G., G.B.), McGill University, Montreal, Canada; Department of Pediatrics (L.G., L.T.T., K.G., G.B.), McGill University, Montreal, Canada; Division of Clinical and Metabolic Genetics and Division of Neurology (L.G., G.Y.), The Hospital for Sick Children, University of Toronto, Toronto, Canada; Department of Child Neurology (F.K.C., M.S.V.D.K., N.I.W.), Emma Children's Hospital, Amsterdam University Medical Centers, Vrije Universiteit Amsterdam, and Amsterdam Neuroscience, Amsterdam, The Netherlands; Department of Clinical Genetics (F.K.C., R.M.V.S.), VU University Medical Center, Amsterdam, The Netherlands; Department of Human Genetics (F.K.C.), Center for Biomedical Research, Diponegoro University, Semarang, Indonesia; Department of Pediatrics (L.S.), Faculty of Medicine, University of Szeged, Szeged, Hungary; Child Health and Human Development Program (L.T.T., K.G., G.B.), Research Institute of the McGill University Health Center, Montreal, Canada; Division of Medical Genetics, Department of Specialized Medicine (L.T.T., K.G., G.B.), McGill University Health Center, Montreal, Canada; Centre de Référence Neurogénétique (F.H., C.G.), Service de Génétique, CHU Bordeaux, Bordeaux, France; Department of Pediatrics (E.L.F.), Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China; Developmental Neurology Department (S.D.A.), Fondazione IRCCS Istituto Neurologico C. Besta, Milan, Italy; Neuroscience and Neurorehabilitation Department (G.V.), Bambino Gesu Children's Hospital, Rome, Italy; Center for Pediatric Genomic Medicine (I.T.), Children's Mercy Hospitals and Clinics, Kansas City, MO; University of Missouri-Kansas City School of Medicine (I.T.), Kansas City, MO; Department of Pathology and Laboratory Medicine (I.T.), Children's Mercy Hospitals, Kansas City, MO; Department of Pediatrics (D.M.N.), Section of Medical Genetics, Ochsner for Children, New Orleans, LA; GeneDx (R.P.), Gaithersburg, MD; Division of Neurology (K.S.L.), Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ; Department of Pediatric Neurology (E.W.), Birmingham Children's Hospital, Birmingham, United Kingdom; Department of Medical Genetics (T.P.), Telemark Hospital, Skien, Norway; Department of Paediatric Neurology (P.F.), St Georges University Hospital NHS Foundation Trust, London, United Kingdom; Clinical Genetics Service (M.M.), St George's University Hospitals NHS Foundation Trust, London, United Kingdom; Clinical Genetics Department (J.R.), Royal Devon and Exeter Hospital NHS Trust, Exeter, United Kingdom; Department of Neurology and Neurosurgery (R.W.), The Children's Hospital at Westmead, Westmead, New South Wales, Australia; Center of Developmental Neurology (H.P.), Frankfurt, Germany; Department of Neurology (B.V.D.W.), Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Neurology (D.T.), Essen University Hospital, University of Duisburg-Essen, Essen, Germany; Department of Clinical Genetics (A.D., C.S.), Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom; Wellcome Sanger Institute (DDD Study), Wellcome Genome Campus, Cambridge, United Kingdom; Department of Pediatrics (N.T.), Division of Child Neurology, University of Texas Health Science Center, Houston, TX, United States of America; Movement Disorders Center and Neurogenetics Research Program (M.C.K.), Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ; Program in Neuroscience (M.C.K.), Arizona State University, Tempe, AZ, United States of America; Division of Neurology (S.S.), Department of Pediatrics, Lady Hardinge Medical College and Associated Kalawati Saran Children's Hospital, New Delhi, India; Division of Neurology (A.V.), Children's Hospital of Philadelphia, Philadelphia, PA; Department of Neurology (A.V.), Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States of America; Department of Child Neurology (D.T.), Neurological Institute C. Besta Foundation IRCCS, Milan, Italy; Department of Functional Genomics (M.S.V.D.K.), VU University, Amsterdam, The Netherlands; Unit of Neuromuscular and Neurodegenerative Disorders (E.B.), Laboratory of Molecular Medicine, Bambino Gesu Children's Hospital, Rome, Italy; Laboratoire MRGM, INSERM U1211, University Bordeaux, Bordeaux, France; Université de Bordeaux (S.F.), INSERM U1212, CNRS 5320, Bordeaux, France; and Department of Human Genetics (G.B.), McGill University, Montreal, Canada.
Objective:
To determine the clinical, radiologic, and molecular characteristics of RNA polymerase III-related leukodystrophy (POLR3-HLD) caused by biallelic POLR1C pathogenic variants.
Methods:
A cross-sectional observational study involving 25 centers worldwide was conducted. Clinical and molecular information was collected on 23 unreported and previously reported patients with POLR3-HLD and biallelic pathogenic variants in POLR1C. Brain MRI studies were reviewed.
Results:
Fourteen female and 9 male patients aged 7 days to 23 years were included in the study. Most participants presented early in life (birth to 6 years), and motor deterioration was seen during childhood. A notable proportion of patients required a wheelchair before adolescence, suggesting a more severe phenotype than previously described in POLR3-HLD. Dental, ocular, and endocrine features were not invariably present (70%, 50%, and 50%, respectively). Five patients (22%) had a combination of hypomyelinating leukodystrophy and abnormal craniofacial development, including 1 individual with clear Treacher Collins syndrome (TCS) features. Brain MRI revealed hypomyelination in all cases, often with areas of pronounced T2 hyperintensity corresponding to T1 hypointensity of the white matter. Twenty-nine different pathogenic variants (including 12 new disease-causing variants) in POLR1C were identified.
Conclusions:
This study provides a comprehensive description of POLR3-HLD caused by biallelic POLR1C pathogenic variants based on the largest cohort of patients to date. These results suggest distinct characteristics of POLR1C-related disorder, with a spectrum of clinical involvement characterized by hypomyelinating leukodystrophy with or without abnormal craniofacial development reminiscent of TCS.
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