MELAS: A Multigenerational Impact of the MTTL1 A3243G MELAS Mutation
Background:
the maternally inherited MTTL1 A3243G mutation in the mitochondrial genome causes MelaS (Mitochondrial encephalopathy lactic acidosis with Stroke-like episodes), a condition that is multisystemic but affects primarily the nervous system. Significant intra-familial variation in phenotype and severity of disease is well recognized.
Methods:
retrospective and ongoing study of an extended family carrying the MTTL1 A3243G mutation with multiple symptomatic individuals. tissue heteroplasmy is reviewed based on the clinical presentations, imaging studies, laboratory findings in affected individuals and pathological material obtained at autopsy in two of the family members.
Results:
there were seven affected individuals out of thirteen members in this three generation family who each carried the MTTL1 A3243G mutation. the clinical presentations were varied with symptoms ranging from hearing loss, migraines, dementia, seizures, diabetes, visual manifestations, and stroke like episodes. three of the family members are deceased from MelaS or to complications related to MelaS.
Conclusions:
the results of the clinical, pathological and radiological findings in this family provide strong support to the current concepts of maternal inheritance, tissue heteroplasmy and molecular pathogenesis in MelaS. neurologists (both adult and paediatric) are the most likely to encounter patients with MelaS in their practice. genetic counselling is complex in view of maternal inheritance and heteroplasmy. newer therapeutic options such as arginine are being used for acute and preventative management of stroke like episodes.
Insights
The MTTL1 A3243G mutation causes MELAS (Mitochondrial encephalopathy lactic acidosis with Stroke-like episodes), with varied symptoms and severity even within families. This study highlights maternal inheritance and heteroplasmy in a multi-generational family.
Area of Science:
- Genetics and Molecular Biology
- Neurology
- Mitochondrial Diseases
Background:
- The maternally inherited MTTL1 A3243G mutation in mitochondrial DNA causes MELAS (Mitochondrial encephalopathy lactic acidosis with Stroke-like episodes).
- MELAS is a multisystemic disorder primarily affecting the nervous system.
- Significant intra-familial variation in phenotype and disease severity is a known characteristic of MELAS.
Purpose of the Study:
- To investigate the clinical manifestations, inheritance patterns, and molecular pathogenesis of MELAS within an extended family.
- To correlate tissue heteroplasmy with clinical presentations in individuals carrying the MTTL1 A3243G mutation.
Main Methods:
- Retrospective and ongoing study of a three-generation extended family with the MTTL1 A3243G mutation.
- Review of clinical presentations, neuroimaging, laboratory findings, and autopsy data from affected individuals.
- Analysis of tissue heteroplasmy in relation to observed clinical phenotypes.
Main Results:
- Seven out of thirteen family members carrying the MTTL1 A3243G mutation exhibited symptomatic MELAS.
- Clinical presentations were diverse, including hearing loss, migraines, dementia, seizures, diabetes, visual disturbances, and stroke-like episodes.
- Three deceased family members had MELAS or complications related to the condition.
Conclusions:
- Findings support current understanding of maternal inheritance, tissue heteroplasmy, and molecular pathogenesis in MELAS.
- Neurologists are likely to encounter MELAS patients; genetic counseling is complex due to inheritance and heteroplasmy.
- Emerging therapies, such as arginine, show promise for managing stroke-like episodes in MELAS.
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