It is one of the cerebral organic acidaemia
, which lacks general metabolic derangements like hypoglycaemia, metabolic acidosis or hyperammonaemia seen in inherited metabolic disorders presenting with metabolic decompensation.
Hyperammonaemia is a metabolic disturbance of the urea cycle characterised by an excess of ammonia in the blood.(1) Hyperammonaemia may develop soon after birth (early onset), or in childhood, adolescence or adulthood (late onset) and can be inherited or acquired.(2) Urea cycle disorders are extremely rare with an overall prevalence estimated at 1:8,000-1:44,000 births.(3) However, these values may be underestimated due to under-diagnosis, misdiagnosis and absent neonatal screening programmes.(3) Organic acidaemias
are also rare, with a European prevalence estimated at 1:29,000-1:65,000(4).
These cases represent over 60% of all IMDs diagnosed in this period and the majority fall into 3 main categories, namely the organic acidaemias
(OAs), the urea cycle defects (UCDs) and the mitochondrial cytopathies.
* metabolic diseases such as Wilson's disease, alpha 1 antitrypsin deficiency, Crigler-Najjar syndrome, and other inborn errors of metabolism (tyrosinaemia, hyperoxaluria, organic acidaemias