SCAD Deficiency

Introduction

Short chain acyl-CoA dehydrogenase (SCAD) deficiency is one type of fatty acid oxidation disorder (FAOD). If you or your loved one is diagnosed with this disorder, you are probably looking for answers. With the help of our founder, Jerry Vockley, we are breaking down exactly what to expect with this diagnosis and what it means for the future.

What Is SCAD Deficiency?

Short chain acyl-CoA dehydrogenase deficiency is one of a group of inherited protein alterations that affects the mitochondria’s ability to generate cellular energy from fats during times of stress, illness, and fasting. In children, the first step in the final round of breaking down fats is reduced or missing. Fortunately, this loss of function toward the end of the process means that the SCAD defect usually has less impact than other fatty acid oxidation disorders that occur earlier in the process.

Genetics

This fatty acid disorder occurs when an individual inherits one mutation in the gene for SCAD (ACADS) from each parent. There are two common SCAD alterations that change the active protein but still leave it with sufficient activity to function without causing illness. Some rare mutations cause a greater loss of protein function and a higher accumulation of butrylcarnitine and ethylmalonic acid, but still rarely cause illness. There is one rare mutation inherited with one of the common alterations that usually results in an intermediate loss of activity.

Signs and Symptoms of MTP/LCHAD Deficiency

Most children and adults with SCAD mutations do not show any specific symptoms. Earlier reported clinical findings of research on fatty acid oxidation have included:

  • Episodes of intermittent metabolic acidosis
  • Coma from elevated blood ammonia (hyperammonemic coma)
  • Neonatal acidosis with elevated muscle tone (hyperreflexia)
  • Multicore muscle breakdown (myopathy) and muscle fat storage with failure to thrive
  • Poor muscle tone (hypotonia)

Unlike other fat oxidation disorders, SCAD deficiency does not cause low blood sugar (hypoglycemia) or low ketones (hypoketosis).

How to Diagnose MTP/LCHAD Deficiency

Today, the majority of SCAD patients in the U.S. are identified right after birth by the expanded newborn screening program. A blood spot is obtained from the infant’s heel and sent to a laboratory for screening before the infant goes home from the birthing facility. The diagnosis involves an analysis of two fat products, butrylcarnitine and ethylmalonic acid, that tend to accumulate in the blood and urine of infants with this deficiency. Because pure SCAD alterations are considered benign, many newborn screening programs no longer report infants with butrylcarnitine elevations, especially those with lesser changes. Because butrylcarnitine and ethylmalonic acid can accumulate in other metabolic defects besides SCAD, infants or children with symptoms of FAODs, along with increased levels of these two metabolites may be referred for further study to rule out other metabolic syndromes.

Treatment

At present, this deficiency is considered a benign condition with no characteristic symptoms that need to be treated.

Investigational Therapies and Fatty Acid Oxidation Research 

At the International Network for Fatty Acid Oxidation Research and Management (INFORM), we suggest finding more information on current clinical trials at ClinicalTrials.gov. This website will have studies from both private and government-funded studies.

If you or your loved one was diagnosed with one of these fatty acid oxidation disorders, our fatty acid oxidation disorders support group is here to help. The goal of INFORM is to educate and connect you to the latest research involving these disorders.

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