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Nonketotic hyperglycinemia presenting with pin-point pupils and hyperammonemia
R Schiffmann1, A Boneh, Z Ergaz
1Pediatric Neurology Unit, Hadassah University Hospital, Mt. Scopus, Jerusalem, Israel.
Insights
Two siblings with lethargy and seizures were diagnosed with nonketotic hyperglycinemia. Pin-point pupils and transient hyperammonemia were key indicators of this rare metabolic disorder.
Area of Science:
- Biochemistry
- Genetics
- Pediatric Neurology
Background:
- Nonketotic hyperglycinemia (NKH) is a rare autosomal recessive metabolic disorder.
- It results from a defect in the glycine cleavage system, leading to glycine accumulation.
- NKH typically presents in neonates with severe neurological symptoms.
Observation:
- Two siblings presented with neonatal onset of lethargy, poor feeding, respiratory distress, and seizures.
- Both infants exhibited characteristic pinpoint pupils.
- Elevated glycine levels in plasma and cerebrospinal fluid (CSF) with abnormal CSF/plasma ratios confirmed NKH.
Findings:
- Amino acid analysis revealed significant glycine accumulation, diagnostic of nonketotic hyperglycinemia.
- Transient hyperammonemia was observed in both siblings, resolving within 72 hours.
- Urine organic acid analysis did not show abnormalities, ruling out other metabolic disorders.
Implications:
- Pinpoint pupils may represent an underrecognized clinical sign of nonketotic hyperglycinemia.
- Early detection of transient hyperammonemia can aid in diagnosing NKH.
- This case highlights the importance of comprehensive metabolic screening in neonates with neurological symptoms.
Abstract:
We describe two siblings who presented with lethargy, decreased sucking, respiratory failure and seizures in their first days of life. Pin-point pupils were noted in both siblings. Amino acid analysis revealed elevated concentrations of glycine in plasma and cerebrospinal fluid (CSF), with abnormal CSF/plasma ratios, compatible with hyperglycinemia. Urine organic acid analysis was unremarkable. Hyperammonemia was found in both siblings, but this subsided within 24-72 h. We suggest that pin-point pupils may be an additional presenting sign of nonketotic hyperglycinemia and, if looked for early enough, hyperammonemia may be found in this disorder.