Understanding LCHAD Deficiency: Basics & Biology

Receiving a diagnosis of LCHAD deficiency (Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase deficiency) can feel overwhelming, especially if it arrived through a routine newborn screening or a sudden medical emergency. It is important to know that while this is a serious condition, understanding the biology behind it is the first step in protecting your child’s health. With early detection and careful management, the focus shifts from a “scary unknown” to a manageable daily routine ^[1].

The Energy Factory: Why Fat Matters

To understand LCHAD, it helps to think of the body’s energy system. Most of the time, our bodies run on sugar (glucose). However, when we go a long time without eating (fasting) or when we are sick, the body switches to burning fat for fuel.

In children with LCHAD deficiency, the body cannot finish the process of breaking down long-chain fats—the type of fat found in most oils and many foods ^[2]. This happens because of a specific “hiccup” in the mitochondria, which are the power plants of every cell in the body ^[3].

The Biological Mechanism: The MTP Complex

LCHAD is part of a larger team of enzymes called the Mitochondrial Trifunctional Protein (MTP) complex ^[2]. This complex is responsible for the final steps of breaking down long-chain fats into energy.

• The Gene: The instructions for building the part of this team that handles LCHAD are found on the HADHA gene ^[3].
• The Subunit: Specifically, the HADHA gene creates the alpha subunit of the MTP complex ^[2].

When there is a mutation in the HADHA gene, the LCHAD enzyme doesn’t work correctly. This leads to two major problems:

1. Energy Shortage: The body cannot produce enough energy from fat, leading to dangerously low blood sugar (hypoglycemia) during periods of fasting or illness ^[4].
2. Toxic Buildup: Instead of being fully broken down, the fats stop halfway through the process. These partially broken-down fats, called long-chain 3-hydroxy fatty acids, begin to build up in the blood and organs ^[5].

How Buildup Affects the Body

These “halfway-broken” fats are toxic to the body’s tissues. If they accumulate, they can cause damage in several areas:

• The Heart: The heart is an organ that relies heavily on fat for energy. A buildup of toxic intermediates can cause cardiomyopathy (weakening of the heart muscle) ^[6].
• The Liver: Toxic fats can lead to liver enlargement or dysfunction, a process sometimes called lipoapoptosis (cell death caused by fat buildup) ^[5].
• The Muscles: During a crisis, muscle tissue can break down (rhabdomyolysis), releasing a protein called myoglobin that can be hard on the kidneys ^[4].
• The Eyes: Over time, the buildup may affect the retina, leading to retinopathy (vision changes), which is why regular eye exams are vital ^[7].

How LCHAD is Diagnosed

Most babies are now identified through Newborn Screening. This is done using a technology called tandem mass spectrometry (MS/MS), which scans the blood for specific markers ^[8].

• Markers: Doctors look for high levels of 3-hydroxy-acylcarnitines, specifically markers labeled as C16-OH, C18-OH, and C18:1-OH ^[8][9].
• Confirmation: Because screening is just a “first look,” doctors must confirm the diagnosis using molecular genetic testing to find the specific mutation in the HADHA gene ^[1][10].

A Note on Pregnancy

Interestingly, LCHAD deficiency in a baby can sometimes cause health issues for the mother during pregnancy. This is because the toxic fats produced by the fetus can enter the mother’s bloodstream ^[5]. If the mother experienced HELLP syndrome (high blood pressure and liver issues) or Acute Fatty Liver of Pregnancy (AFLP), it may have been an early sign of the baby’s LCHAD deficiency ^[11][3].

While your child will always be metabolically fragile—meaning they require a strict diet and cannot fast for long periods—early diagnosis is a life-saving tool that allows your medical team to prevent these crises before they begin ^[1][12].