Primary carnitine deficiency is an inherited (genetic) condition that prevents the body from breaking down certain fats and turning them into energy.

OCTN2 is a protein in your body that allows a type of fat called fatty acids to be processed. OCTN2 is a special protein that acts as a transporter. It brings a substance called carnitine into your cells. Your body needs carnitine to use or break down fatty acids.

Without enough OCTN2 transporter, your baby's cells do not have enough carnitine. That results in difficulty using fats for energy. This condition can be more or less severe depending on much of the OCTN2 transporter your baby can make.

Breaking down fat for energy allows the body to work properly, and it is especially important after a long time without food (fasting) and during illness. If your body does not make enough energy from fat, blood sugar levels can become dangerously low.

When fats are not processed, waste (including toxins) can build up and damage your liver, heart, and muscles. If untreated, the lack of energy and increased toxins lead to the signs and symptoms of the condition. Severe cases that are not treated early can result in heart problems, coma, or death.

Primary carnitine deficiency is a genetic condition. Babies inherit it from their biological (birth) parents.

• Primary carnitine deficiency is an autosomal recessive condition. Babies inherit it when each parent passes down a nonworking SLC22A5 gene to their baby. Only babies with two nonworking SLC22A5 genes—one from the mom and one from the dad—have this condition.
  • People with one working copy and one nonworking copy of the SLC22A5 gene are called carriers.
  • Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
  • If two parents are carriers of a nonworking copy of the SLC22A5 gene, they have a 1 in 4 chance of having a child with primary carnitine deficiency.
  • Carriers for primary carnitine deficiency often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with primary carnitine deficiency.
  • Parents who already have a child with primary carnitine deficiency still have a 1 in 4 chance of having another child with primary carnitine deficiency. This 1 in 4 chance stays the same for future children.
• Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it.

Signs of primary carnitine deficiency can vary widely and may appear anytime from a few months of age to childhood. Common illnesses, like a cold or flu, or going a long time without food can trigger symptoms.

Signs of the condition may include the following:

• Unusual behavior due to the brain not working properly
• Weak or enlarged heart (cardiomyopathy)
• Low blood sugar (hypoglycemia)
• Enlarged liver (hepatomegaly)
• Poor feeding
• Gets upset or confused easily
• Weakness
• Tiredness or lack of energy (lethargy)

Newborn screening for primary carnitine deficiency is done using a small amount of blood collected from your baby’s heel. During screening, a special machine measures how much carnitine is in your baby’s blood. Babies with low levels of carnitine might have primary carnitine deficiency.

What Happens After an Out-of-Range Screening Result?

If your baby’s blood spot screening result for primary carnitine deficiency is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.

An out-of-range screening result does not mean that your baby definitely has the condition. It does mean that your baby needs more follow-up testing.

Your baby may need the following tests after an out-of-range screening result:

• Blood and/or urine tests
• Genetic testing using a blood sample

You should complete any recommended follow-up testing as soon as possible. Babies with this condition can have serious health problems if they are not diagnosed and treated quickly.

False-positive newborn screening results for this condition are rare. Babies who are born early (premature) may have out-of-range results. Also, screening samples collected too early (before the baby is 24 hours old) may affect the results of screening.

Some babies might have a false-positive out-of-range result for primary carnitine deficiency because their mother has low carnitine levels. These babies do not have and will not develop primary carnitine deficiency but can still have low blood carnitine test results. More testing on both mom and baby will determine who has low carnitine levels.

Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need to get treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.

It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.

Treatments may include the following:

• Regular and frequent meals and snacks
• Diet high in carbohydrates and low in fat
• L-carnitine supplements to help the body break down fats
• People with primary carnitine deficiency must be very careful during illnesses that cause poor appetite, vomiting, or diarrhea. During these illnesses, people with this condition may need emergency care and intravenous (IV) treatments to prevent dangerously low blood sugar levels.

Children who receive early and ongoing treatment for primary carnitine deficiency can have healthy growth and development.