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Primary Hyperoxaluria Type 1 with Homozygosity for a Double-mutated AGXT Allele in a 2-year-old Child
S Krishnamurthy1, G B Kartha1, V S Venkateswaran1
1Department of Pediatrics, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
Insights
Primary hyperoxaluria Type 1, a rare genetic disorder, was identified in a South Indian child. Molecular testing revealed two novel mutations in the AGXT gene, potentially causing a more severe condition.
Area of Science:
- Genetics
- Biochemistry
- Pediatrics
Background:
- Primary hyperoxaluria Type 1 (PH1) is a rare genetic disorder.
- It results from a deficiency in the liver enzyme alanine-glyoxylate aminotransferase (AGT), encoded by the AGXT gene.
Observation:
- A 2-year-old South Indian child presented with nephrocalcinosis, a hallmark of PH1.
- Genetic analysis revealed a homozygous genotype with two missense mutations in the AGXT gene: c.32C>G (p.Pro11Arg) and c.167T>A (p.Ile56Asn).
Findings:
- This is the first molecularly confirmed case of childhood-onset PH1 in South India.
- The patient's AGXT allele carried two distinct missense mutations, a previously unreported occurrence.
Implications:
- The co-occurrence of two mutations on a single AGXT allele may lead to a more severe PH1 phenotype.
- This case highlights the importance of comprehensive genetic testing for rare diseases and understanding genotype-phenotype correlations.
Abstract:
Primary hyperoxaluria (PH) Type 1 is a rare, genetic disorder caused by deficiency of the liver enzyme alanine-glyoxylate aminotransferase, which is encoded by AGXT gene. We report a 2-year-old South Indian Tamil child with nephrocalcinosis due to PH Type 1, in whom a homozygous genotype for two missense mutations in the AGXT gene was found: first, a C to G transversion (c. 32C>G) in exon 1 resulting in the amino acid substitution p.Pro11Arg; second, a T to A transversion (c. 167T>A) in exon 2 resulting in p.Ile56Asn. A therapy based on potassium citrate and pyridoxine was started. This is the first report of molecular testing-proven childhood onset-PH Type 1 from South India and is notable for the co-occurrence of two missense mutations in one AGXT allele, which might lead to different and more severe phenotype than each mutation alone. To the best of our knowledge, AGXT allele carrying two already known mutations has not been previously reported.
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