Inborn Errors of Metabolism: Could Your Baby Inherit a Hidden Health Risk from You?

Most babies are born healthy, but some may carry invisible genetic conditions that can quietly cause serious health problems. Thanks to modern technology, expecting and new parents can detect these conditions early — and give their child the best possible start.

WORDS LIM TECK CHOON

Expanded newborn screening is becoming a vital tool in modern prenatal and newborn care, to help detect a group of genetic conditions called inborn errors of metabolism (IEM) before they turn life-threatening to the newborn.

WHAT ARE INBORN ERRORS OF METABOLISM (IEM)?

FEATURED EXPERT DR CH’NG TONG WOOI Consultant Paediatric Endocrinologist and Paediatrician Sunway Medical Centre

• Dr Ch’ng Tong Wooi explains that inborn errors of metabolism are a group of rare genetic disorders where the body can’t properly break down certain proteins, fats, or sugars.
• She asserts that IEM is not caused by the mother’s habits during her pregnancy or poor parenting. “IEM is written into the baby’s genetic code,” she says.
• If left undetected, some of these conditions can cause severe complications like developmental delays, organ damage, or even death.

Some Examples of IEM

Phenylketonuria (PKU)

• The affected person lacks the enzyme needed to digest an amino acid, phenylalanine.
• Because of this, the person can experience a wide range of issues ranging from nerve issues to intellectual disability.
• Once expended newborn screening confirms the presence of PKU, the affected person will have to be placed on medications and/or a diet that has restricted amounts of phenylalanine.

Galactosemia

• The affected person cannot digest a sugar called galactose, which is commonly present in milk.
• In infants, galactosemia can lead to organ damage and mental disabilities, even death,
• Affected person will have to go on a galactose-free diet. They may also need additional therapy and support for learning disabilities, stunted growth, and/or balance and mobility issues.

Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency

• The affected person is unable to digest certain fats.
• They tend to have severe lack of energy and tiredness and are prone to having blood sugar levels drop dangerously low (hypoglycaemia).
• They can also experience complications that can lead to liver disease, coma, and other serious health problems.
• In the US, newborns are routinely tested for MCAD deficiency at birth.

As we can see, these conditions can be managed or treated when detected early. This is where genetic services can be of use.

HOW GENETIC SERVICES CAN HELP

FEATURED EXPERT PROFESSOR DR THONG MEOW KEONG Visiting Consultant Clinical Geneticist Sunway Medical Centre

• By analyzing a person’s genes, specialists can identify whether someone carries a faulty gene linked to an inherited condition.
• In prenatal settings, this typically involves carrier screening for both parents.
• A carrier is someone who carries a genetic mutation for a recessive condition but doesn’t have any symptoms themselves.

A Deeper Dive into How Someone Can Inherit a Condition from Their Parents

To better understand how genetic services can help, let’s first take a closer look at how certain attributes, or traits, are passed down from parent to child.

When it comes to inherited conditions, it depends on whether the trait is dominant or recessive.

• A dominant trait needs just one mutated gene from either parent to show up in the child.
• A recessive trait causes problems if a child inherits two copies of the faulty gene — one from each parent. If a child gets just one, they’ll be a carrier: perfectly healthy but still able to pass that gene down to their own kids one day.

However, Not Everything Comes from Mum or Dad

• Some genetic conditions do not follow these classic inheritance rules.
• They can happen because of random changes in a baby’s genetic material, without being passed down from either parent.
• These are called spontaneous genetic errors — rare, unpredictable, and nobody’s fault.

Genetic Counselling Before or During Pregnancy (Prenatal Genetic Counselling)

“Prenatal genetic counselling helps parents understand the risks of passing on inheritable conditions to their children, what tests are available, and what the results might mean for their family,” says Professor Dr Thong Meow Keong.

Newborn Screening

For newborns, expanded newborn screening for IEM uses a simple blood test, usually taken via a heel prick, to check for several rare metabolic conditions.

• This simple test can detect more than 40 potentially life-threatening IEMs.
• Results are available within 2 to 3 working days after the sample reaches the lab.
• The screening typically covers a range of disorders, including:
  • Amino acid disorders (like phenylketonuria — PKU)
  • Organic acid disorders
  • Fatty acid oxidation disorders

Why Go Through the Trouble When These Conditions are Rare?

• While these conditions are individually rare, but when combined, they affect an estimated 150 out of 500,000 newborns in Malaysia every year.
• While Malaysia doesn’t yet have extensive local data for all IEM conditions, disorders like glucose-6-phosphate dehydrogenase (G6PD) deficiency — a condition affecting the body’s ability to handle certain medications and foods — are fairly common here.

How Does Early Detection Help?

• Many IEMs require a special diet, medication, or regular monitoring, while others might involve more intensive interventions.
• Professor Dr Thong points out that, by detecting a problem early before the child becomes unwell, parents and doctors have the opportunity to prevent further complications with tailored treatment and management plans for their child.

“It’s about giving a child the chance at a normal, healthy life — something every parent wants,” he says.

FINAL THOUGHTS

Genomic services are about giving families options, clarity, and control in situations where ignorance could cost dearly.

As genetic testing technology becomes more accessible and affordable, it’s a conversation worth having — whether you’re expecting a baby or planning for one.