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What are we screening for?

 

Metabolic disorders in the Newborn Metabolic Screening Programme


The Newborn Metabolic Screening Programme currently screens for 28 metabolic disorders:

  • Amino acid disorders (14 disorders, including PKU and MSUD) 
  • Fatty acid oxidation disorders (9 disorders)
  • Others: 
    • Congenital hypothyroidism (CH)
    • Cystic fibrosis (CF)
    • Congenital adrenal hyperplasia (CAH)
    • Galactosaemia
    • Biotinidase deficiency.

If your baby has one of these disorders, you will receive information about the disorder and how to treat it from a paediatrician. For more information see the pamphlet Your Newborn Baby's Blood Test.

What are metabolic disorders?


Metabolic disorders are rare inherited disorders in which pathways that produce certain biochemicals malfunction. These pathways are like assembly lines in a human cell. A blockage at any point along the assembly line can lead to a build-up of toxic chemicals in the cell or lack of an important biochemical in the body.
Nearly every metabolic disorder has several forms, which vary in age of onset, clinical severity and mode of inheritance. Many lead to major organ dysfunction or failure. Without treatment, their presentation ranges from mild disorders to acute life-threatening diseases.

Table of disorders with cause, treatment, and incidences


The disorders, cause, treatment and incidence rates for New Zealand are:

 Disorder

 Cause

 Treatment

 Incidence

Congenital hypothyroidism The thyroid is missing, not functioning or in the wrong place. Can lead to slow growth and developmental delay.  Medication (thyroid hormone)

1 in 4,000 babies (about 15 babies a year)

Cystic fibrosis A defective gene and its protein product leads to thick sticky mucus. Medication Physiotherapy 1 in 7,000 babies (about 8 babies a year)
Amino Acid disorders (14 disorders*)
eg Phenylketonuria (PKU)
 An enzyme is missing.
eg PKU - without this enzyme an amino acid (called phenylalanine) rises to harmful levels and can lead to developmental delay.
 Special diet 1 in 12,000 babies (about 5 babies a year)
Fatty acid oxidation disorders (9 disorders**)
eg Medium chain acyl-CoA dehydrogenase deficiency or MCADD
 An enzyme is missing.
Without these enzymes energy cannot be converted from fats and can lead to coma and death.
 Regular feeding (avoidance of fasting)  1 in 12,000 babies (about 5 babies a year)
Congenital Adrenal  Hyperplasia (CAH) An enzyme is missing in the adrenal gland. In severe forms leads to ambiguous genitalia in girls and salt/hormonal imbalances in both sexes. Steroid   medication 1 in 20,000 babies (about 3 babies a year)
Galactosemia A defective enzyme prevents normal use of milk sugar leading to jaundice, cataracts and life-threatening illness. Special diet 1 in 100,000 (about 1 baby every 2 years)
Biotinidase deficiency An enzyme is missing resulting in a deficiency in biotin. This deficiency can lead to seizures, hearing loss and developmental delay. Vitamin H (biotin) 1 in 150,000 (about 1 baby every 3 years)

*Other amino acid disorders include:

  • Argininosuccinic aciduria (argininosuccinate lyase deficiency)
  • Citrullinaemia (argininosuccinate synthetase deficiency, citrin deficiency)
  • Glutaric acidaemia type I (glutaryl-CoA dehydrogenase deficiency)
  • Homocystinuria (cystathionine beta-synthase deficiency)
  • 3-Hydroxy-3-methylglutaryl-CoA lyase deficiency (HMGCoA lyase deficiency)
  • Isovaleric acidaemia (isovaleryl-CoA dehydrogenase deficiency)
  • Beta-ketothiolase deficiency (mitochondrial acetoacetyl-CoA thiolase deficiency)
  • 3-Methylcrotonyl-CoA carboxylase deficiency
  • Methylmalonic acidurias (mutase deficiency, CblA, CblB, CblC, CblD defects)
  • Multiple carboxylase deficiency (holocarboxylase synthetase deficiency)
  • Propionic acidaemia (propionyl-CoA carboxylase deficiency)
  • Tyrosinaemia  (fumaryl acetoacetase deficiency, tyrosine aminotransferase deficiency).


**Fatty acid oxidation disorders include:

  • CACT (carnitine acylcarnitine translocase deficiency)
  • Carnitine transporter defect
  • CPT-I (carnitine palmitoyltransferase-I deficiency)
  • CPT-II (carnitine palmitoyltransferase-II deficiency)
  • LCHAD (3-hydroxy long-chain acyl-CoA dehydrogenase deficiency)
  • TFP (trifunctional protein deficiency)
  • MADD (multiple acyl-CoA dehydrogenase deficiency)
  • MCAD (medium-chain acyl-CoA dehydrogenase deficiency)
  • VLCAD (very-long-chain acyl-CoA dehydrogenase deficiency).