Severe CNS bleeding followed by a good clinical outcome in the acute neonatal form of isovaleric acidaemia

Management and emergency treatments of neonates with a suspicion of inborn errors of metabolism

During the neonatal period, inborn errors of metabolism mostly present with an overwhelming illness that requires prompt diagnosis and both supportive and specific treatments. The most frequent situations are due to branched-chain organic acidurias that present with ketoacidosis and urea cycle defects that are characterized by hyperammonaemia. During both situations, toxin removal procedures and nutritional support with a free-protein and high-energy diet are pivotal treatments. In patients presenting with hypoglycaemia blood glucose levels must be corrected. Progress following glucose provision is useful in recognizing the disorders that are mainly implicated. Hyperinsulinism requires high-glucose infusion. Glycogen storage diseases and gluconeogenesis defects are easily treated with a permanent glucose provision while hypoglycaemias quickly recur. In patients with galactosaemia, hereditary fructose intolerance or tyrosinaemia type I, the presentation is dominated by a liver failure requiring galactose and fructose exclusion associated with a low-protein diet. Many patients with beta-oxidation defects may present with hypoglycaemia that is usually easily corrected. The precise diagnosis can be easily missed in those patients that do well in the following weeks but may develop cardiac failure, arrhythmia and/or liver failure. Patients presenting with intractable convulsions, vitamin responsiveness to biotin, pyridoxine and folate must be considered.

Branched-chain organic acidurias

Branched chain organic acidurias are a group of disorders that result from an abnormality of specific enzymes involving the catabolism of branched chain amino acids (leucine, isoleucine, valine). Maple syrup urine disease (MSUD), isovaleric acidaemia (IVA), propionic aciduria (PA) and methylmalonic aciduria (MMA) represent the most commonly encountered abnormal organic acidurias. All these four disorders present in neonates as a neurologic distress of the intoxication type with either ketosis or ketoacidosis and hyperammonaemia. There is a free interval between birth and clinical symptoms. MMA, PA and IVA present with a severe dehydration, leuconeutropenia and thrombopenia which can mimic sepsis. All these disorders can be diagnosed by identifying acylcarnitine and other organic acid compounds in plasma and urine by gas chromatography mass spectrometry or tandem MS-MS. These disorders are amenable to treatment by removing toxic compounds and by using special diets and carnitine.