Infantile hepatocerebral syndromes associated with mutations in the mitochondrial DNA polymerase-gammaA
Gianfrancesco Ferrari1, Eleonora Lamantea, Alice Donati
1Unit of Molecular Neurogenetics, Pierfranco and Luisa Mariani Center for the Study of Children's Mitochondrial Disorders, National Institute of Neurology, Milano, Italy.
Insights
Mutations in the POLG1 gene cause Alpers disease and other severe mitochondrial disorders in infants. These genetic defects lead to progressive neurological and liver failure, highlighting POLG1
Area of Science:
- Genetics
- Neurology
- Hepatology
Background:
- Mitochondrial disorders are a group of debilitating diseases often caused by genetic mutations.
- Alpers' hepatopathic poliodystrophy is a severe, progressive neurological and hepatic condition affecting infants.
- The POLG1 gene encodes a key enzyme in mitochondrial DNA replication.
Observation:
- Nine infant patients presented with progressive neurological and hepatic failure.
- Eight patients were diagnosed with Alpers' hepatopathic poliodystrophy, while one had floppy infant syndrome and liver failure.
- Genetic analysis revealed distinct allelic mutations in the POLG1 gene in all affected infants.
Findings:
- The POLG1 gene is a significant contributor to mitochondrial disorders.
- Mutations in POLG1 can lead to mitochondrial DNA (mtDNA) deletions, depletion, or point mutations.
- These molecular changes result in a wide range of clinical presentations, from mild to fatal.
Implications:
- Identifying POLG1 mutations is crucial for diagnosing severe infant mitochondrial diseases.
- Understanding the genotype-phenotype correlations in POLG1 mutations can aid in predicting disease progression.
- This research underscores the importance of genetic testing in cases of unexplained neurological and hepatic failure in infants.
Abstract:
We studied nine infant patients with a combination of progressive neurological and hepatic failure. Eight children, including two sibling pairs and four singletons, were affected by Alpers' hepatopathic poliodystrophy. A ninth baby patient suffered of a severe floppy infant syndrome associated with liver failure. Analysis of POLG1, the gene encoding the catalytic subunit of mitochondrial DNA polymerase, revealed that all the patients carried different allelic mutations in this gene. POLG1 is a major disease gene in mitochondrial disorders. Mutations in this gene can be associated with multiple deletions, depletion or point mutations of mitochondrial DNA (mtDNA). In turn, these different molecular phenotypes dictate an extremely heterogeneous spectrum of clinical outcomes, ranging from adult-onset progressive ophthalmoplegia to juvenile ataxic syndromes with epilepsy, to rapidly fatal hepatocerebral presentations, including Alpers' syndrome.
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