Is Systemic Primary Carnitine Deficiency Hereditary?

Systemic Primary Carnitine Deficiency (SPCD) is a hereditary condition, meaning it is passed down through families. However, having SPCD does not automatically mean your children will also have the condition. SPCD follows an inheritance pattern known as autosomal recessive, which means a person must inherit two copies of the mutated gene—one from each parent—to develop the disease ^[1].

The Role of the SLC22A5 Gene

SPCD is caused by mutations in a specific gene called SLC22A5 ^[1]. This gene provides instructions for making a protein known as OCTN2, which acts as a transporter to bring carnitine into your cells ^[2]. You may sometimes see SPCD referred to as “OCTN2 deficiency” in your medical records.

Everyone has two copies of the SLC22A5 gene.

• If you have SPCD, both of your SLC22A5 genes have mutations.
• A carrier is someone who has one mutated copy of the gene and one normal copy. Carriers typically do not have symptoms of SPCD because their one normal gene produces enough of the OCTN2 transporter protein ^[1].

Your Chances of Passing SPCD to Your Children

If you have SPCD, the likelihood of your children inheriting the condition depends entirely on the genetics of the other biological parent.

• If the other parent is not a carrier: All of your children will inherit one mutated gene from you and one normal gene from the other parent. This means 100% of your children will be carriers, but none of them will have SPCD ^[1].
• If the other parent is a carrier: For each pregnancy, there is a 50% chance the child will have SPCD (inheriting a mutated gene from both of you) and a 50% chance the child will be a carrier (inheriting the mutated gene from you and the normal gene from the other parent) ^[1].

If you are planning a family, your partner can undergo genetic carrier testing for the SLC22A5 mutation to help determine the exact risk to your future children ^[3].

Inheritance Risks for Family Members

Because SPCD is genetic, your biological relatives also have a risk of carrying or having the condition. If two carriers have a child (such as a sibling who is a carrier and their partner who is also a carrier), there is a 25% chance their child will have SPCD, a 50% chance the child will be a carrier, and a 25% chance the child will not inherit the mutation at all ^[1].

If you are diagnosed with SPCD, it is highly recommended that your first-degree relatives—parents, siblings, and children—are screened ^[4][5]. Even if they feel fine, they could be asymptomatic carriers or have a mild, undiagnosed form of SPCD. Early diagnosis in family members can prevent serious, life-threatening complications ^[6].

Managing Pregnancy and Maternal Health

If you have SPCD, pregnancy requires careful medical management. Your body’s carnitine levels can naturally fluctuate or drop during pregnancy, which may increase the risk of maternal symptoms or metabolic stress ^[7]. It is critical to work with your medical team to closely monitor your carnitine levels and potentially adjust your L-carnitine supplementation dose to ensure both you and your baby remain safe ^[7].

Newborn Screening and Early Treatment

Newborn screening, often done via a heel-prick blood test, can quickly identify if a baby has SPCD ^[8]. This is critical because early, prompt treatment with L-carnitine supplementation is highly effective at preventing symptoms and complications like cardiomyopathy ^[9][10].

Interestingly, newborn screening sometimes leads to a mother’s initial diagnosis. Because a baby’s carnitine levels at birth reflect the mother’s levels, a low carnitine result in a healthy newborn often uncovers that an asymptomatic mother actually has SPCD ^[7].