Differential diagnosis and mechanism of primary and secondary hyperammonaemia (HA)11 79 81
| Increased ammonia production | |
| Condition | Suggested mechanism |
| Exercise/seizures/trauma | AMP deamination |
| Gastric bypass/starvation | Increased protein catabolism |
| GI haemorrhage Total parenteral nutrition | Excess protein/nitrogen load |
| Infections with urease-producing bacteria | Urinary tract infection, with relevant organisms splitting urea to form ammonia |
| Decreased ammonia elimination | |
| Acute or chronic liver disease | Reduced urea cycle, glutamine synthesis; portosystemic shunt |
| Urea cycle disorder | Enzyme block or substrate transport affecting urea cycle |
| Fatty acid disorder of oxidation | Lack of acetyl-CoA leading to reduced CPS1 activity |
| Organic acidaemia | NAGS inhibition by relevant increased acid |
| Carbonic anhydrase Va deficiency | Lack of bicarb leading to reduced CPS1 |
| Mitochondrial disorders | Impaired ATP production/substrate |
| Ornithine aminotransferase deficiency | Lack of ornithine affecting OTC, urea cycle defects |
| Glutamine synthase deficiency | Decreased glutamine and hence ammonia clearance |
| Lysinuric protein intolerance | Lack of urea cycle ornithine and arginine |
CPS1, carbamoylphosphate synthetase; GI, gastrointestinal ; NAGS, N-acetylglutamate synthetase; OTC, ornithine transcarbamylase.