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Brain Dev. 2014 Mar;36(3):259-63. doi: 10.1016/j.braindev.2013.03.006. Epub 2013 May 3.

Different patterns of cerebellar abnormality and hypomyelination between POLR3A and POLR3B mutations.

Author information

1
Department of Pediatrics, Kameda Medical Center, Kamogawa, Japan; Department of Radiology, Toho University Sakura Medical Center, Sakura, Japan. Electronic address: jtaka44@hotmail.co.jp.
2
Division of Neurology, Clinical Research Institute, Kanagawa Children's Medical Center, Yokohama, Japan.
3
Department of Human Genetics, Yokohama City University, Graduate School of Medicine, Yokohama, Japan.
4
Department of Child Neurology, National Center of Neurology and Psychiatry, Kodaira, Japan.
5
Department of Radiology, The University of Tokyo, Tokyo, Japan.
6
Department of Neurology, Kameda Medical Center, Kamogawa, Japan.
7
Division of Neurology, Saitama Children's Medical Center, Saitama, Japan.
8
Segawa Neurological Clinic for Children, Tokyo, Japan.
9
Department of Neurology, The University of Tokyo, Tokyo, Japan.
10
Department of Mental Retardation and Birth Defect Research, National Center of Neurology and Psychiatry, Kodaira, Japan.
11
Department of Radiology and Biomedical Imaging, University of California San Francisco, CA, USA.

Abstract

BACKGROUND:

Mutations of POLR3A and POLR3B have been reported to cause several allelic hypomyelinating disorders, including hypomyelination with hypogonadotropic hypogonadism and hypodontia (4H syndrome).

PATIENTS AND METHODS:

To clarify the difference in MRI between the two genotypes, we reviewed MRI in three patients with POLR3B mutations, and three with POLR3A mutations.

RESULTS:

Though small cerebellar hemispheres and vermis are common MRI findings with both types of mutations, MRI in patients with POLR3B mutations revealed smaller cerebellar structures, especially vermis, than those in POLR3A mutations. MRI also showed milder hypomyelination in patients with POLR3B mutations than those with POLR3A mutations, which might explain milder clinical manifestations.

CONCLUSIONS:

MRI findings are distinct between patients with POLR3A and 3B mutations, and can provide important clues for the diagnosis, as these patients sometimes have no clinical symptoms suggesting 4H syndrome.

KEYWORDS:

Cerebellum; Diffuse cerebral hypomyelination with cerebellar atrophy and hypoplasia of the corpus callosum (HCAHC); Hypomyelination; Hypomyelination with hypogonadotropic hypogonadism and hypodontia (4H syndrome); MRI; POLR3A; POLR3B; RNA polymerase III (Pol III)

PMID:
23643445
DOI:
10.1016/j.braindev.2013.03.006
[Indexed for MEDLINE]
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