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Neurology. 2016 Apr 26;86(17):1622-6. doi: 10.1212/WNL.0000000000002612. Epub 2016 Mar 30.

Diffuse hypomyelination is not obligate for POLR3-related disorders.

Author information

1
From the Laboratory of Neurogenetics of Motion (R.L.P.) and Department of Neuroradiology (R.L.P.), Montreal Neurological Institute and Hospital, and the Departments of Neurology and Neurosurgery (R.L.P., L.T.T., K.G., G.B.) and Pediatrics (R.L.P., L.T.T., K.G., G.B.), McGill University, Montreal, Canada; Departments of Child Neurology (F.K.C., M.S.v.d.K., N.I.W.) and Clinical Genetics (F.K.C., R.v.S.), VU University Medical Center, Amsterdam, the Netherlands; Department of Genetics (K.Õ.) United Laboratories, Tartu University Hospital, Tartu; Department of Pediatrics (K.Õ.), University of Tartu, Estonia; Institute of Human Genetics (T.H.), Technische Universität München; Institute of Human Genetics (T.H.), Helmholtz Zentrum München, Munich, Germany; Department of Neurology (E.W.), Birmingham Children's Hospital, UK; Department of Neurology (D.T.), University Clinic Essen, University of Duisburg-Essen, Germany; Department of Child and Adolescent Neurology (H.M.), Institute of Mother and Child, Warsaw, Poland; Department of Child Neurology (B.T.P.), AMC Academic Medical Center, Amsterdam, the Netherlands; West Midlands Regional Clinical Genetics Unit (C.P., H.C.), Birmingham Women's Hospital, UK; Departments of Pediatrics (T.A.) and Medical Genetics (H.O.), Faculty of Medicine (F.O.), Ege University, Izmir, Turkey; Department of Neurology (A.V.), Children's National Health System, Washington, DC; Neuroscience Campus Amsterdam (M.S.v.d.K., N.I.W.), the Netherlands; and Department of Medical Genetics (G.B.), Montreal Children's Hospital, McGill University Health Center, Montreal, Canada.
2
From the Laboratory of Neurogenetics of Motion (R.L.P.) and Department of Neuroradiology (R.L.P.), Montreal Neurological Institute and Hospital, and the Departments of Neurology and Neurosurgery (R.L.P., L.T.T., K.G., G.B.) and Pediatrics (R.L.P., L.T.T., K.G., G.B.), McGill University, Montreal, Canada; Departments of Child Neurology (F.K.C., M.S.v.d.K., N.I.W.) and Clinical Genetics (F.K.C., R.v.S.), VU University Medical Center, Amsterdam, the Netherlands; Department of Genetics (K.Õ.) United Laboratories, Tartu University Hospital, Tartu; Department of Pediatrics (K.Õ.), University of Tartu, Estonia; Institute of Human Genetics (T.H.), Technische Universität München; Institute of Human Genetics (T.H.), Helmholtz Zentrum München, Munich, Germany; Department of Neurology (E.W.), Birmingham Children's Hospital, UK; Department of Neurology (D.T.), University Clinic Essen, University of Duisburg-Essen, Germany; Department of Child and Adolescent Neurology (H.M.), Institute of Mother and Child, Warsaw, Poland; Department of Child Neurology (B.T.P.), AMC Academic Medical Center, Amsterdam, the Netherlands; West Midlands Regional Clinical Genetics Unit (C.P., H.C.), Birmingham Women's Hospital, UK; Departments of Pediatrics (T.A.) and Medical Genetics (H.O.), Faculty of Medicine (F.O.), Ege University, Izmir, Turkey; Department of Neurology (A.V.), Children's National Health System, Washington, DC; Neuroscience Campus Amsterdam (M.S.v.d.K., N.I.W.), the Netherlands; and Department of Medical Genetics (G.B.), Montreal Children's Hospital, McGill University Health Center, Montreal, Canada. genevieve.bernard@mcgill.ca.

Abstract

OBJECTIVE:

To report atypical MRI patterns associated with POLR3A and POLR3B mutations.

METHODS:

This was a multicenter retrospective study to collect neuroradiologic, clinical, and molecular data of patients with mutations in POLR3A and POLR3B without the classic MRI phenotype, i.e., diffuse hypomyelination associated with relative T2 hypointensity of the ventrolateral thalamus, globus pallidus, optic radiation, corticospinal tract at the level of the internal capsule, and dentate nucleus, cerebellar atrophy, and thinning of the corpus callosum.

RESULTS:

Eight patients were identified: 6 carried mutations in POLR3A and 2 in POLR3B. We identified 2 novel MRI patterns: 4 participants presented a selective involvement of the corticospinal tracts, specifically at the level of the posterior limbs of the internal capsules; 4 patients presented moderate to severe cerebellar atrophy. Incomplete hypomyelination was observed in 5 participants.

CONCLUSION:

Diffuse hypomyelination is not an obligatory feature of POLR3-related disorders. Two distinct patterns, selective involvement of the corticospinal tracts and cerebellar atrophy, are added to the MRI presentation of POLR3-related disorders.

PMID:
27029625
PMCID:
PMC4844237
DOI:
10.1212/WNL.0000000000002612
[Indexed for MEDLINE]
Free PMC Article

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