M/SCHAD: Medium/Short Chain L-3-hydroxyacyl-CoA Dehydrogenase Deficiency

Medium/short-chain L-3-hydroxy acyl-CoA dehydrogenase deficiency is a type of genetic condition where too much insulin goes into the blood, which causes low blood sugar levels. M/SCHAD deficiency is also part of a group of genetic conditions called familial hyperinsulinism (also known as congenital hyperinsulinism/CHI or persistent hyperinsulinemic hypoglycemia of infancy/PHHI). The body usually gets its energy by breaking down, or burning, fats and sugars. People with FAODs cannot properly break down certain types of fats. This prevents the body from creating needed energy during times of stress, illness, fasting, and exercise, which can lead to medical symptoms.

M/SHAD deficiency

HADHSC, HADH

• Autosomal recessive

People usually have two copies of the HADHSC gene (sometimes called the HADH gene), one inherited from each parent. M/SCHAD deficiency occurs when there are changes in both copies of the HADHSC gene (autosomal recessive inheritance). Someone who has a change in only one copy of the HADHSC gene is called a carrier, and they usually do not have any medical symptoms. If both parents are carriers, there is a 1 in 4 chance with each pregnancy that their child will have M/SCHAD deficiency.

M/SCHAD deficiency is very rare, and the exact frequency is unknown.

Both Male and Female

M/SCHAD deficiency can cause a range of signs and symptoms. Whether your child was diagnosed via newborn screening may also affect when, if, and how these symptoms present. Always check with your doctor if your child is doing something out of “their” normal, as every child may present with symptoms a little differently.

Signs and symptoms may include:

• Extreme sleepiness (lethargy)
• Irritability
• Poor appetite
• Mood changes

Without treatment, people with M/SCHAD deficiency can have additional signs and symptoms including:

• Low blood sugar (hypoglycemia)
• Fever
• Diarrhea
• Vomiting
• Coma and seizures
• Breathing problems
• Low blood sugar (hypoglycemia)
• Fever
• Diarrhea
• Vomiting
• Coma and seizures
• Breathing problems

Most cases of M/SCHAD deficiency are identified by routine newborn screening. If newborn screening is suggestive of M/SCHAD deficiency, additional tests may be performed including:

• Measuring biochemical markers in the blood or urine
• Measuring M/SCHAD protein activity from skin cell samples (cultured fibroblasts)
• Performing a genetic test to look for changes in the HADHSC gene

If there is a known family history of M/SCHAD deficiency, or if parents know they are known carriers, prenatal testing can be performed.

Yes

Treatment and management of M/SCHAD deficiency includes:

• Regular eating schedules to prevent low blood sugar (hypoglycemia)
• Medication called diazoxide to reduce insulin levels in the blood
• Intravenous (IV) sugar-containing fluids called D10 during a metabolic crisis

Parents should call their healthcare provider immediately if babies show symptoms like excessive sleepiness, vomiting, diarrhea, a fever, poor appetite, or an infection. Medical treatment should be sought immediately if there is loss of consciousness or severe confusion (decompensation), as these are signs of dangerously low blood sugar.

Patients should discuss the appropriate preparation for anesthesia with their metabolic team.

• 3-alpha hydroxyacyl-CoA dehydrogenase deficiency – About the Disease – The  National Institutes of Health
• M/SCHAD Deficiency | Fatty Acid Oxidation Disorders Diagnosis – The INFORM Network
• Conditions Medium/Short-Chain L-3 Hydroxyacyl-CoA Dehydrogenase Deficiency – Baby’s First Test

Connecting with others impacted by a rare disease allows for vital information to be shared about day-to-day life, prevents isolation, and gives hope. Please contact MitoAction for peer support opportunities at 888-MITO-411 or email mito411@mitoaction.org.

Other resources we recommend are:

• New Patient Kit for Mitochondrial Conditions
• Planning for Emergencies
• Monthly Expert Series
• Energy in Action Podcast