1. A patient with pontocerebellar hypoplasia type 6 : Novel RARS2 mutations, comparison to previously published patients and clinical distinction from PEHO syndrome
- Author
-
Henna Tyynismaa, Anni Laari, Anna-Elina Lehesjoki, Viivi Nevanlinna, Anna-Kaisa Anttonen, Taru Hilander, Leena Valanne, Mikko Muona, Svetlana Konovalova, Katarin Gorski, Berten Ceulemans, Carolina Courage, Centre of Excellence in Stem Cell Metabolism, STEMM - Stem Cells and Metabolism Research Program, Henna Tyynismaa / Principal Investigator, University of Helsinki, Research Programs Unit, Molecular and Integrative Biosciences Research Programme, Department of Medical and Clinical Genetics, Medicum, HUS Medical Imaging Center, Department of Diagnostics and Therapeutics, HUSLAB, Anna-Elina Lehesjoki / Principal Investigator, Neuroscience Center, Helsinki Institute of Life Science HiLIFE, and Mitochondrial Morphogenesis
- Subjects
Proband ,Male ,Pathology ,Microcephaly ,Brain Edema ,0302 clinical medicine ,Cerebellum ,PEHO syndrome ,Pontocerebellar hypoplasia type 6 ,Frameshift Mutation ,Genetics (clinical) ,0303 health sciences ,TBCD ,1184 Genetics, developmental biology, physiology ,Nuclear Proteins ,Neurodegenerative Diseases ,Progressive cerebellar and cerebral atrophy ,General Medicine ,Arginine-tRNA Ligase ,Magnetic Resonance Imaging ,Hypsarrhythmia ,Hypotonia ,3. Good health ,Phenotype ,Olivopontocerebellar Atrophies ,Muscle Hypotonia ,Cerebellar atrophy ,medicine.symptom ,Spasms, Infantile ,medicine.medical_specialty ,PROGRESSIVE ENCEPHALOPATHY ,Pontocerebellar hypoplasia ,Mutation, Missense ,RARS2 ,03 medical and health sciences ,Atrophy ,Seizures ,Intellectual Disability ,Genetics ,medicine ,Humans ,Alleles ,030304 developmental biology ,Epilepsy ,business.industry ,OPTIC ATROPHY ,Infant ,EDEMA ,medicine.disease ,Human medicine ,3111 Biomedicine ,business ,030217 neurology & neurosurgery ,Transcription Factors - Abstract
Pontocerebellar hypoplasia type 6 (PCH6) is a rare infantile-onset progressive encephalopathy caused by biallelic mutations in RARS2 that encodes the mitochondrial arginine-tRNA synthetase enzyme (mtArgRS). The clinical presentation overlaps that of PEHO syndrome (Progressive Encephalopathy with edema, Hypsarrhythmia and Optic atrophy). The proband presented with severe intellectual disability, epilepsy with varying seizure types, optic atrophy, axial hypotonia, acquired microcephaly, dysmorphic features and progressive cerebral and cerebellar atrophy and delayed myelination on MRI. The presentation had resemblance to PEHO syndrome but sequencing of ZNHIT3 did not identify pathogenic variants. Subsequent whole genome sequencing revealed novel compound heterozygous variants in RARS2, a missense variant affecting a highly conserved amino acid and a frameshift variant with consequent degradation of the transcript resulting in decreased mtArgRS protein level confirming the diagnosis of PCH6. Features distinguishing the proband's phenotype from PEHO syndrome were later appearance of hypotonia and elevated lactate levels in blood and cerebrospinal fluid. On MRI the proband presented with more severe supratentorial atrophy and lesser degree of abnormal myelination than PEHO syndrome patients. The study highlights the challenges in clinical diagnosis of patients with neonatal and early infantile encephalopathies with overlapping clinical features and brain MRI findings.
- Published
- 2020