Symptoms & Diagnosis of VLCAD

Learning about the symptoms of VLCAD deficiency and how it is diagnosed can help families better understand the condition. Below you will find an overview of common symptoms and the tests doctors use to confirm a diagnosis.

Common Symptoms of VLCAD

Symptoms of VLCAD can vary from person to person. Some individuals may experience only mild symptoms, while others may have more serious complications. Common VLCAD symptoms may include:

Hypoglycemia

Hypoglycemia occurs when blood sugar levels drop too low because the body cannot properly break down long-chain fats for energy. In VLCAD, the body is unable to produce enough ketones as an alternative fuel during fasting, sleep, or illness. This condition is called hypoketotic hypoglycemia. Symptoms may include shakiness, irritability, sweating, dizziness, fatigue, and difficulty concentrating. Early recognition and consistent nutrition are important for preventing complications.

Rhabdomyolysis

Rhabdomyolysis, also known as rhabdo, occurs when muscle tissue breaks down and releases proteins into the bloodstream. This can happen when the body does not have enough energy, particularly during illness or intense physical activity. Symptoms may include severe muscle pain, muscle weakness, tip-toe walking, dark-colored urine, and extreme fatigue. Because rhabdomyolysis can lead to serious complications affecting the kidneys and overall health, prompt medical care is important if these symptoms occur.

Cardiomyopathy

Cardiomyopathy is a condition that affects the heart muscle. In some individuals with VLCAD, the heart may not receive enough energy to work efficiently. When the heart muscle becomes weakened or enlarged, it can have difficulty pumping blood effectively throughout the body. Symptoms may include shortness of breath, fatigue, poor feeding in infants, or swelling in the legs or abdomen. Regular monitoring by healthcare providers, including heart evaluations, helps detect cardiomyopathy early and ensure proper care.

Lethargy

Lethargy refers to extreme tiredness or low energy levels. Because the body has difficulty converting stored fat into energy in VLCAD, individuals may feel unusually fatigued, especially during illness, fasting, or periods of increased activity. This can appear as excessive sleepiness, difficulty staying alert, or reduced interest in normal activities. Maintaining regular meals, following medical nutrition guidelines, and monitoring during illness can help support healthy energy levels and reduce the risk of severe fatigue.

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Did You Know?

VLCAD deficiency exists on a spectrum, meaning symptoms and severity can vary from person to person. Some individuals may experience frequent symptoms, while others may only have issues during illness, fasting, or intense activity. Symptoms can also change over time, appearing differently during various stages of life.

Because each person with VLCAD may respond differently, not every warning sign will look the same. Even if a symptom is not commonly listed, it may still be a trigger or early warning sign for your loved one. Keeping notes about symptoms you notice, especially if they occur more than once, can be helpful. Sharing this information with your healthcare team may help you recognize patterns and respond more quickly to potential metabolic crises.

Inside the body, there are tiny helpers called enzymes that break down nutrients into energy. One of these enzymes is responsible for processing long-chain fatty acids, which are a major source of fuel during times when the body is not eating.

In VLCAD deficiency, this specific enzyme does not work properly due to a genetic change in the ACADVL gene. Without enough enzyme activity, the body struggles to convert stored fat into energy. As a result, the body may run out of fuel more quickly than expected, especially during sleep, illness, missed meals, or increased activity.

When the body cannot access enough energy, it may cause:

  • Low blood sugar (hypoglycemia)

  • Muscle weakness or muscle breakdown (rhabdomyolysis)

  • Fatigue and low energy tolerance (lethargy)

  • Heart complications (cardiomyopathy) in some individuals

This is why consistent nutrition, medical monitoring, and specialized care are so important for people living with VLCAD.

How VLCAD Affects the Body’s Energy?

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Diagnosis VLCAD Deficiency

Early diagnosis of Very Long-Chain Acyl-CoA Dehydrogenase (VLCAD) deficiency is important so children can receive the proper nutrition, monitoring, and medical care needed to stay healthy. Many individuals with VLCAD are diagnosed shortly after birth through routine screening, while others may be diagnosed later if symptoms appear.

Doctors use several tests to confirm a diagnosis of VLCAD and understand how the condition may affect the body.

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  • In many countries, VLCAD deficiency is detected through newborn screening, a routine blood test performed within the first few days after a baby is born. A small sample of blood is taken from the baby’s heel and analyzed to look for signs of metabolic conditions that affect how the body processes nutrients.

    Newborn screening can detect abnormal levels of certain fatty acids that suggest the body may not be breaking down long-chain fats properly. If the screening test shows possible signs of VLCAD, doctors will order additional testing to confirm the diagnosis.

    Early detection through newborn screening is extremely important because it allows families and healthcare providers to begin monitoring and care before serious symptoms develop.

  • To confirm VLCAD deficiency, doctors often perform genetic testing. This test looks for changes in the ACADVL gene, which provides instructions for making the enzyme needed to break down long-chain fatty acids for energy.

    Genetic testing can confirm whether a person has VLCAD deficiency and may also help determine the specific type or severity of the condition. Because VLCAD is an inherited genetic disorder, genetic testing can also help identify family members who may be carriers of the condition.

    Understanding the genetic cause of VLCAD helps doctors develop a personalized care plan and provides important information for family planning.

  • In some situations, doctors may recommend additional testing to better understand how the body’s enzymes are functioning. One possible test is a muscle biopsy, where a small sample of muscle tissue is examined in a laboratory.

    This test can help specialists evaluate how well the body is able to process fatty acids and produce energy. However, muscle biopsies are used less often today because genetic testing and other metabolic tests can usually confirm the diagnosis.

    Metabolic specialists may also perform blood and urine tests to evaluate how the body processes fats and responds during illness or fasting.

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You can access FREE genetic testing through the following programs:

Early diagnosis of VLCAD deficiency is important because it allows families and healthcare providers to begin management strategies that help prevent complications. These strategies may include maintaining regular meals and avoiding long periods without food, following specialized nutrition recommendations, monitoring closely during illness or increased physical activity, and working with metabolic specialists and healthcare providers. With early diagnosis and proper care, many individuals with VLCAD can live healthy and active lives.