Glucose 6 Phosphate Dehydrogenase (G6PD) Deficiency
 

Throughout the treatment, the newborns must be well-hydrated to help the kidneys

Newborns with G6PD deficiency are always kept longer in the hospital for at least five days for signs of severe jaundice

G6PD deficiency is a significant cause of mild to severe jaundice in newborns
 
By Than Soo Nyet

Glucose 6 phosphate dehydrogenase (G6PD) deficiency is a disorder that is significant among newborns. It causes severe unconjugated hyperbilirubinaemia (neonatal jaundice) and results in brain damage if not detected and treated early. All newborns in Malaysian public hospitals have their cord blood sent for test to detect this condition while still in the labour room, since it is a hospital policy that no newborns are allowed to be discharged without knowing the results. Those newborns with G6PD deficiency are always kept longer in the hospital, for at least five days, for signs of severe jaundice (Hussain & Ng, 2005).

G6PD deficiency is a genetic disorder that occurs most often in males, very often the first born. In Malaysia, the overall incidence of G6PD deficiency among males is 3.1 %, more prevalent among Chinese and Malays than among Indians (Ainoon et al., 2003). This condition mainly affects red blood cells. In affected newborn, a defect in an enzyme called glucose-6-phosphate dehydrogenase causes red blood cells to break down prematurely when exposed to oxidants or when certain foods or herbs are ingested. This destruction of red blood cells is called haemolysis.

This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located in the X chromosome, one of the two sex chromosomes. In males (one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (two X chromosomes), a mutation must occur in both copies of the gene to cause the disorder. Because of the unlikelihood of females having two altered copies of this gene, males are thus more frequently affected by the X-linked recessive disorders. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

The most common medical problem associated with G6PD deficiency is haemolytic anaemia, which occurs when red blood cells are destroyed faster than the body can replace them. This type of anaemia leads to jaundice - yellowing of the skin and whitening of the eyes, dark urine and fatigue.

G6PD deficiency is a significant cause of mild to severe jaundice in newborns as the newborn’s liver is incapable of coping with the excessive amount of bilirubin formed as a result of rapid haemolysis. Our body has two types of bilirubins: conjugated and unconjugated bilirubin. Conjugated bilirubin forms after being conjugated by hepatic enzymes to become water soluble excreted in faeces and urine. However, unconjugated bilirubin, due to a lack of hepatic enzymes, is fat soluble and cannot be excreted from the body. Highly toxic when the level is high, it becomes a known neurotoxin with affinity for brain cells. Among newborns, the resulting high level of unconjugated bilirubin results in convulsion, kernicterus and brain damage. But the liver’s ability to cope in older children and adults, will not normally cause much damage if early blood transfusion is given for the anaemia.

For newborns, unconjugated hyperbilirubinaemia can be treated with phototherapy and exchange transfusion (Maisels & McDonagh, 2008). Phototherapy is a form of light therapy to place naked newborns under light. The light helps to convert the bilirubin to water soluble form. Throughout the treatment, the newborns must be well-hydrated to help the kidneys excrete excess bilirubin. Blood transfusion is only resorted to when the level of unconjugated bilirubin is dangerously high. This treatment involves the tedious process of exchanging the baby’s blood with donated fresh whole blood via a catheter inserted into the umbilical artery of the newborn. Thus 50% of the unconjugated bilirubin in the baby’s blood is quickly removed within two hours compared to the phototherapy that would take several days to do so. However, this procedure carries more risks to the baby compared to phototherapy.

Parents of a newborn with G6PD deficiency are advised on the prevention of triggering the onset of red blood cell destruction (haemolysis) throughout the life span of their child. Red blood cell destruction can be triggered by infections, severe stress, certain foods such as fava beans or kacang parang, and certain drugs, including anti-malarial drugs, Quinidine, Quinine, aspirin, nitrofurantoin, nonsteroidal, anti-inflammatory drugs (NSAIDs), and sulfonamides. Other chemicals, such as those in mothballs, can also trigger an episode. Therefore when newborns are discharged from hospitals, parents are advised to remove all mothballs in the house and given a list of agents (see Table 1) to avoid in the future. This list must be shown to the doctor whenever the child needs medical attention to prevent a possible wrong prescription by the doctor.

For parents with G6PD child, extra care has to be taken in the child's diet to ensure that all caretakers, paediatricians and school teachers are well-informed of the condition. With the right precautions, a child with G6PD deficiency can lead a healthy and active life.

Agents to be avoided in G6PD Deficiency Patients
Foods and Herbs to be avoided
  • Fava Beans (Kacang Parang)
  • Documented Chinese herbs / medicine
  • Chuen Lin
  • San Chi
  • 13 herbs
  • 12 herbs
  • Other traditional herbs / medications are also not to be taken unless with medical advice
Other chemicals to be avoided
  • Naphthalene (moth balls)
  • Mosquito coils and insect repellants which contains pyrethium
Drugs to be avoided or contraindicated
  • Acetanilide
  • Doxorubicin
  • Furazolidone
  • Methylene Blue
  • Nalidixic acid
  • Niridazole
  • Nitrofurantoin
  • Phenazopyridine
  • Primaquine
  • Sulfamethoxazole
  • Bactrim

Drugs that can be safely given in therapeutic doses
  • Paracetamol
  • Ascorbic Acid
  • Aspirin
  • Chloramphenicol
  • Chloroquine
  • Colchicine
  • Diphenhydramine
  • Isoniazid
  • Phenacetin
  • Phenylbutazone
  • Phenytoin
  • Probenecid
  • Procainamide
  • Pyrimethamine
  • Quinidine
  • Streptomycin
  • Sulfisoxazole
  • Trimethoprim
  • Tripelennamine
  • Vitamin K
  • Mefloquine
 
Table 1: Source Paediatric Protocols For Malaysian Hospitals, Ministry of Health, Malaysia.
 
In conclusion, early detection of G6PD deficiency among newborns can help reduce the incidence of mental retardation due to brain damage caused by unconjugated hyperbilirubinaemia. Careful observations for signs of jaundice, early and prompt treatment of resulting unconjugated hyperbilirubinaemia in newborns, should be the responsibility of all members of the medical team working in the maternal and paediatric units, as well as those in the community.

Since mental retardation can only be detected when the child is older, the government should consider introducing the National At -Risk Register for all babies with a history of jaundice, as practiced in the United Kingdom. This is to monitor the children up to their school age to detect the extent of brain damage as in the form of slow learners, neural deafness, behaviour problems and spasticity.  The mass media also need to create public awareness about this condition.
 
References
  • Ainoon, O., Joyce, N.Y., Boo, N.Y., Cheong, S.K., Zainal, Z.A., and Hamidah, N.H. (2003). G6PD deficiency variants in Malaysian Chinese. Human Mutation, January 21(1):101.
  • Hussain Imam B. Muhammad Ismail, Ng, H. P. (2005) Paediatric protocols for Malaysian hospitals. Kuala Lumpur: Ministry of Health, Malaysia.
  • Maisel, M.J., & McDonagh, A.F. (2008) Phototherapy for neonatal jaundice. New England Journal of Medicine 358:920-928.
 
Last updated: 22 December 2009
     
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