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References OMIM Gene GeneReviews HGMD HGNC
last update : 31-08-2009
Symbol HHH
Location 13q14.11
Name hyperornithinemia-hyperammonemia-homocitrullinuria syndrome
Other name(s) ornithine translocase deficiency
Corresponding gene SLC25A15
Other symbol(s) HHHS
Main clinical features
  • disorder of the urea cycle and ornithine degradation pathway, with pyramidal signs, decreased vibration sense, buccofaciolingual dyspraxia, and learning difficulties or subnormal intelligence found in mostly patients, with anomalies of peripheral nerve conduction velocity and of evoked potentials, rarely, episodes of symptomatic hyperammonemia
  • aversion to protein-rich foods, coagulation abnormalities, hypotonia,
  • developmental delay, progressive encephalopathy with mental regression, and early signs of motor dysfunction, responsive to dietary and pharmacological therapy (Tessa 209)
    Genetic determination autosomal recessive
    Function/system disorder metabolism/aminoacids
    Type disease
    Gene product
    Name ornithine transporter 1 (ORNT1
    Gene mutationChromosome rearrangementEffectComments
    unknown     predominantly mutation F188 delta (French Canadians)
    Genotype/Phenotype correlations genotype cannot predict the phenotype because mitochondrial lineage may contribute to the neuropathophysiology of HHH patients