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Hyperammonemia as a Presenting Feature in Two Siblings with FBXL4 Variants
Sarah U Morton1,2, Edward G Neilan3, Roy W A Peake4
1Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA.
Mutations in the FBXL4 gene cause early-onset mitochondrial encephalomyopathy. New cases reveal hyperammonemia and cerebellar hypoplasia, suggesting anaplerotic therapy may help manage this rare genetic disorder.
Area of Science:
- Genetics
- Biochemistry
- Neurology
Background:
- Early-onset mitochondrial encephalomyopathy is a rare neonatal disorder.
- Sequence variants in the nuclear-encoded gene FBXL4 are a known cause.
- Classic signs include lactic acidosis, hypotonia, and developmental delay.
Purpose of the Study:
- To report two siblings with novel FBXL4 mutations.
- To characterize their unique clinical presentation.
- To expand the understanding of FBXL4-related disorders.
Main Methods:
- Clinical case study of two siblings.
- Biochemical analysis of plasma and urine metabolites.
- Review of previously reported FBXL4 mutation cases.
Main Results:
- Siblings presented with hyperammonemia, low aspartate, and tricarboxylic acid cycle defects.
- Cerebellar hypoplasia was observed alongside classic mitochondrial signs.
- Episodic exacerbations of lactic acidosis and hyperammonemia occurred post-stabilization.
Conclusions:
- These cases expand the phenotypic spectrum of FBXL4 mutations.
- The findings suggest a potential role for anaplerotic therapies.
- FBXL4 mutations represent a significant cause of early-onset mitochondrial disease.
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