U.S. flag

An official website of the United States government

GTR Home > Conditions/Phenotypes > Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome

Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome

Synonyms
HHH syndrome; Ornithine translocase deficiency; Ornithine translocase deficiency syndrome
Modes of inheritance
Autosomal recessive inheritance (Orphanet)

Summary

Excerpted from the GeneReview: Hyperornithinemia-Hyperammonemia-Homocitrullinuria Syndrome
Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a disorder of the urea cycle and ornithine degradation pathway. Clinical manifestations and age of onset vary among individuals even in the same family. Neonatal onset (~8% of affected individuals). Manifestations of hyperammonemia usually begin 24-48 hours after feeding begins and can include lethargy, somnolence, refusal to feed, vomiting, tachypnea with respiratory alkalosis, and/or seizures. Infantile, childhood, and adult onset (~92%). Affected individuals may present with: Chronic neurocognitive deficits (including developmental delay, ataxia, spasticity, learning disabilities, cognitive deficits, and/or unexplained seizures); Acute encephalopathy secondary to hyperammonemic crisis precipitated by a variety of factors; and Chronic liver dysfunction (unexplained elevation of liver transaminases with or without mild coagulopathy, with or without mild hyperammonemia and protein intolerance). Neurologic findings and cognitive abilities can continue to deteriorate despite early metabolic control that prevents hyperammonemia.
Full text of GeneReview (by section):
Summary
Diagnosis
Clinical Characteristics
Genetically Related (Allelic) Disorders
Differential Diagnosis
Management
Genetic Counseling
Resources
Molecular Genetics
Chapter Notes
References
Authors:
Jose Camacho
Natalia Rioseco-Camacho
view full author information

Available tests

90 tests are in the database for this condition.

Check Related conditions for additional relevant tests.

Clinical tests (90 available)

Biochemical Genetics Tests

Molecular Genetics Tests

Genes See tests for all associated and related genes

  • Also known as: D13S327, HHH, LNC-HC, ORC1, ORNT1, SLC25A15
    Summary: solute carrier family 25 member 15

Clinical features

Help
Imported from Human Phenotype Ontology (HPO)

Show allHide all

IMPORTANT NOTE: NIH does not independently verify information submitted to the GTR; it relies on submitters to provide information that is accurate and not misleading. NIH makes no endorsements of tests or laboratories listed in the GTR. GTR is not a substitute for medical advice. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.