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Isolated methylmalonic acidemia: a case report
Tarik Es Sadki1, Stéphanie Badiou1, Mathilde Boubal2
1Laboratoire de biochimie, CHU Montpellier, France.
Abstract:
Isolated methylmalonic acidemia (AMR) is an inborn error of metabolism due to an enzymatic deficit in methylmalonyl-CoA mutase. AMR lead to increased methylmalonic acid in plasma and urine without hyperhomocysteinemia. The clinical signs are recurrent episodes of ketoacidosis and bouts of vomiting, dehydration and mental retardation. These symptoms do not respond to the administration of vitamin B12. We report a case of a ten-months-old infant to whom the diagnosis was suspected in the presence of a metabolic acidosis, hyperammonemia, without hepatic impairment and ketosis. The chromatography of organic acids showed elevated methylmalonic acid levels. Molecular genetics allowed confirming the diagnosis of deficit in methylmalonyl-CoA mutase demonstrating the genetic abnormality of the gene MUT.
Insights
Isolated methylmalonic acidemia (AMR) is a metabolic disorder caused by a methylmalonyl-CoA mutase enzyme deficit. Early diagnosis and genetic confirmation are crucial for managing this condition in infants.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Isolated methylmalonic acidemia (AMR) is an inherited metabolic disorder.
- It results from a deficiency in the methylmalonyl-CoA mutase enzyme.
- AMR is characterized by elevated methylmalonic acid levels without hyperhomocysteinemia.
Observation:
- A ten-month-old infant presented with metabolic acidosis, hyperammonemia, and ketosis.
- Clinical signs included vomiting, dehydration, and developmental delay.
- Symptoms were unresponsive to vitamin B12 administration.
Findings:
- Organic acid chromatography revealed elevated methylmalonic acid levels.
- Molecular genetic analysis confirmed a deficit in the methylmalonyl-CoA mutase enzyme.
- The genetic abnormality was identified in the MUT gene.
Implications:
- This case highlights the importance of suspecting AMR in infants with unexplained metabolic acidosis and hyperammonemia.
- Accurate diagnosis relies on biochemical testing and molecular genetics.
- Understanding the genetic basis of AMR is essential for diagnosis and potential future therapies.
