Hyperornithinemia-hyperammonemia

Hcit homocitrulline, Hey homocysteine, HHH hyperornithinemia-hyperammonemia-homocitrullinemia, His histidine,... 

Hyperornithinemia- Defect in mitochondrial hyperammonemia- transport of ornithine homocitrulhnuiia (HHH syndrome) Disorders of carbohydrate metabolism Hyperornithinemia, hyperammonemia, homocitrullinuria, hyperglutaminemia, hyperalaninemia Ataxia, lethargy, vomiting, choreoathetosis, seizures, coma, developmental delay Protein restriction arginine supplementation None... 

Hyperornithinemia - hyperammonemia - homocitrullinuria Hyperi n sul inis m-hy p eram mo nemi a (H IMA)... 

Consideration of other plasma amino acids also informs the diagnosis of inborn errors of urea synthesis. The plasma concentrations of glutamine and alanine are often elevated in parallel with or prior to the ammonium concentration as they act as a nitrogen buffer. Plasma arginine concentrations are low since the only synthetic route for arginine in humans is via the urea cycle. In contrast, the arginine concentration is elevated in ARG-1 deficiency. Hyperornithinemia and homocitrullinuria are the characteristic features of the hyperammonemia, hyperornithinemia, and homocitrullinuria (HHH) syndrome caused by a defect in the ornithine transporter (ORNT-1). 

Citrulline is exchanged for ornithine across the inner mitochondrial membrane by ORNT-1. Ornithine is produced in the cytosol as the final step in the urea cycle and must be returned to the mitochondrial matrix for transcarbamoyla-tion by OTC. A second ornithine-citrulline antiporter (ORNT-2) is also expressed in the liver mitochondria and may attenuate the severity of disease in patients with HHH (Hyperammonemia, Hyperornithinemia, Homocitrullinuria) disease due to ORNT-1 deficiency. This disorder typically manifests later in life with intermittent hyperammonemic encephalopathy and protein aversion. Intramitochondrial ornithine deficiency causes both hyperammonemia and hyperornithinemia due to a lack of substrate for OTC. Homocitrullinuria occurs due to the use of lysine by OTC as an alternate substrate. The diagnosis is confirmed by mutation analysis. 

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