MCADD (Medium-Chain Acyl-CoA Dehydrogenase Deficiency)
Key Points
If notified of a positive newborn test result for MCADD, the medical home should collaborate with a metabolic geneticist who will help verify the test result and follow through with appropriate care and education for the patient and the family. Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) details initial steps for confirming the diagnosis and immediate management.
Acute decompensation is more common during acute illness, fasting, or other times of metabolic stress. Management revolves around fasting avoidance and prompt treatment of acute episodes with intravenous (IV) glucose. [Feillet: 2012] [Potter: 2012] If untreated, acute attacks of hypoglycemia can rapidly progress to seizures, coma, and sudden death.
Although nonketotic hypoglycemia is a hallmark presentation, some affected individuals can generate some ketones.
Adolescents and adults with MCADD should be counseled about the possible risks of excessive consumption of alcohol, which may include encephalopathy, rhabdomyolysis, and cardiac failure. [Lang: 2009]
All families who have a child with MCADD should have an emergency treatment letter that can be presented at the emergency room in case of illness. A medical alert bracelet or necklace also can be worn to let providers know that the child has MCADD, but it is not a substitution for the emergency letter. See Sample Letter for Emergency Care for the Child with MCADD (Medical Home Portal) (

Children with MCADD who are ill require early evaluation and intervention. During an acute illness, any form of tolerable caloric intake is necessary (e.g., juice, Gatorade, and Powerade). If unable to tolerate oral intake, dextrose-containing IV fluids should be administered to maintain normoglycemia. Occasionally, uncooked cornstarch (1-1½ g/kg) may be recommended by a metabolic provider as a preventative measure for infants and young children. Levocarnitine (50 mg/kg/day) supplementation may also be recommended if experiencing a secondary deficiency.
Hypoglycemia occurs after the onset of clinical symptoms and is an unreliable marker for early decompensation or encephalopathy. Therefore, families should speak with their metabolic provider about the usefulness of home glucose monitoring for them. [Leonard: 2009]
Although fasting tolerance improves with age, prolonged fasting in an affected individual can lead to coma and death at any age. Patients should be counseled to remain hydrated and consume additional calories during prolonged physical activity.
Diagnosis
Presentations
Affected individuals may be asymptomatic until placed under the right amount of metabolic stress. The clinical presentation is indistinguishable from other hypoglycemia causes, including clamminess, irritability, lethargy, and vomiting. They may experience intermittent symptoms after periods of fasting or intercurrent illnesses. Less often, liver disease and hepatomegaly may be presenting features.
Diagnostic Criteria and Classifications
- Positive findings on expanded newborn screening
- Nonketotic hypoglycemia
- Elevations of C8, C6, C10, C10:1 acylcarnitines
- Elevations of urinary dicarboxylic acids, hexanoylglycine, suberylglycine, and cis-4-decenoic acid
- DNA testing identifying the common A985G variant and/or other pathogenic variants in the ACADM gene
Screening & Diagnostic Testing
Laboratory Testing
- Plasma acylcarnitine analysis with elevations of C8, C6, C10, C10:1
- Urine organic acids with elevations of hexanoylglycine, octanoylglycine, decanoylglycine; may also see elevated dicarboxylic acids adipic, suberic, sebacic, and dodecanedioic
- Urine acylglycine with elevations of n-hexanoylglycine, 3-phenylpropionylglycine, and suberylglycine
Genetic Testing
Testing for Family Members
Genetics & Inheritance
Parents of a child with MCADD are counseled that they have a 25% chance of having an affected baby, a 50% chance of having a baby who is a carrier, and a 25% chance of having a baby who is neither affected nor a carrier. Unaffected siblings have a 67% chance of being carriers of the disorder. All of the children of an affected individual will be, at the least, carriers. The probability of having an affected child depends on the carrier status of the other parent.
Prevalence
Differential Diagnosis
Important clinical features that might help differentiate MCADD from the other fatty acid oxidation disorders (e.g., very long-chain acyl-CoA dehydrogenase deficiency, long-chain 3-hydroxylacyl-CoA dehydrogenase deficiency, carnitine palmitoyl transferase I/II deficiencies, carnitine transporter defect, and carnitine translocase deficiency) include the absence of cardiomyopathy and/or rhabdomyolysis, which are common among these other conditions. The biochemical pattern of MCADD is very specific, though, and can be differentiated from other fatty acid oxidation disorders.
Ketogenesis defects
The ketogenesis defects often present within the first few days of life. The pattern of presentation in later childhood and some presenting symptoms, such as vomiting, decreased sensorium, and hepatomegaly, may be very similar to MCADD. Although hypoketotic hypoglycemia and sometimes hyperammonemia are biochemical features, severe ketoacidosis is the rule.
Organic acidurias
Most organic acidurias present with hyperketotic hypoglycemia rather than hypoketotic hypoglycemia.
Carbohydrate metabolism defects
Carbohydrate metabolism defects may present with hypoglycemia, significant lactic acidosis, +/- ketosis, and hepatomegaly. Acylcarnitine profile and urine organic acid profile will help differentiate these disorders from MCADD.
Co-occuring Conditions
Prognosis
Treatment & Management
Endocrine/Metabolism
With prolonged fasting, lipolysis and hepatic fatty acid oxidation become activated. Plasma levels of free fatty acids rise, but ketones remain inappropriately low. Patients then become hypoglycemic with progressive lethargy, confusion, nausea, and vomiting. Hepatomegaly is sometimes noted. Without rapid intervention with IV glucose, hypoglycemia can rapidly progress to seizures, coma, and sudden death.
The following general guidelines are recommended, though they should be taken on a case-by-case basis and not include situations in which there is an extra metabolic stressor:
- Infants should be fed frequently; fasting should not exceed 3 to 4 hours
- Between 6 months and 1 year of age, fasting should not exceed 8 hours
- Between 1 to 2 years of age, fasting should not exceed 10 hours
- For individuals older than 2 years, fasting should not exceed 12 hours
Treatment of ill patients with MCADD involves:
- IV fluid therapy, preferably with D10 (and electrolytes per clinical discretion) at 1.5-2 x maintenance, should be given to maintain normoglycemia.
- If a patient becomes ill, prompt administration of IV glucose is mandatory. Delay in treatment may lead to sudden death or permanent neurologic sequelae. Under no circumstances should the administration of IV glucose be delayed.
- Oral glucose gel or other forms of simple sugars that can be absorbed by the mucus membranes may be kept available for families and used in emergency situations as a temporary solution while seeking medical care.

The use of carnitine is controversial but indicated when there is a secondary carnitine deficiency. [Lee: 2005] If supplementation with carnitine is necessary, it should be initiated under the guidance of the metabolic specialist. It had been recommended that the dose of L-carnitine be 50-100 mg/kg/day.
Nutrition/Growth/Bone
Learning/Education/Schools
Services & Referrals
Refer to a metabolic geneticist who, along with a metabolic nutritionist, will educate the family about the disorder and its treatment. If the diagnosis has not been made but is suspected, refer for testing. Periodic visits are important to support families, monitor for problems, and provide needed education. Refer if supplementation with carnitine is being considered. Consult for management of diet and if the child becomes ill.
The nutritionist will play a critical role in formulating a healthy diet with the necessary fats, carbohydrates, proteins, vitamins, minerals, and cofactors to allow for proper growth and development.
Refer for assistance with genetic testing, interpretation of results, and to discuss inheritance patterns, recurrence risks, and reproductive options for the individual with MCADD and their family.
Refer if indicated by clinical presentation, especially if seizures are part of the initial presentation or persistent.
Referral should be made if there is concern about sequelae after an acute presentation or concern about specific developmental deficits.
ICD-10 Coding
Resources
Information & Support
Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD)
Immediate response to a positive newborn test result.
Developmental Screening
Screening tools and guidance on response to a positive screen.
Formulas andFormulas for Metabolic Conditions (

Fatty Acid Oxidation Disorders (FAQ)
Answers to questions parent may frequently ask about their child with MCADD's care.
For Professionals
MCADD (OMIM)
Information about clinical features, diagnosis, management, and molecular and population genetics; Online Mendelian Inheritance
in Man, authored and edited at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine
Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency (GeneReviews)
Excellent review of MCADD that includes a clinical description, differential diagnoses, management information, and molecular
genetic information; sponsored by the U.S. National Library of Medicine.
Guidelines for MCADD (Genetic Metabolic Dietitians International)
Extensive clinical information about nutrition therapy for MCADD. Topics include background, signs and symptoms, laboratory
findings, biochemical basis of MCADD, chronic and acute management, monitoring, and special circumstances; edited by Dianne
M. Frazier, PhD, MPH, RD.
For Parents and Patients
Fatty Oxidation Disorders (FOD) Family Support Group
Information for families about fatty acid oxidation disorders, support groups, coping, finances, and links to other sites.
MCADD - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by metabolic and genetic specialists, for families who have received
an initial diagnosis of this newborn disorder; Screening, Technology and Research in Genetics.
Medium-chain acyl-CoA dehydrogenase deficiency (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources;
from the National Library of Medicine.
MCADD: A Guide for Parents (PacNoRGG) ( 618 KB)
Eight-page guide that includes an overview, social concerns, sample treatment plan, glossary, regional resources, and references;
sponsored by the Pacific Northwest Regional Genetics Group.
MCADD: A Guide for Parents (PacNoRGG) (Spanish) ( 202 KB)
Spanish translation of an 8-page guide that includes an overview, social concerns, sample treatment plan, glossary, regional
resources, and references; sponsored by the Pacific Northwest Regional Genetics Group.
Tools
Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) (NECMP) ( 17 KB)
Guideline for clinicians treating the sick infant or child who has MCADD; developed under the direction of Dr. Harvey Levy,
Senior Associate in Medicine/Genetics at Children’s Hospital Boston, and Professor of Pediatrics at Harvard Medical School,
for the New England Consortium of Metabolic Programs. Click pdf to view the complete protocol.
Sample Letter for Emergency Care for the Child with MCADD (Medical Home Portal) ( 14 KB)
A sample letter with emergency treatment details that can be provided to families who have a child with MCADD.
ACT Sheet for MCADD (C8-C6-C10) (ACMG) ( 348 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical
Genetics.
Confirmatory Algorithm for MCAD Deficiency ( 170 KB)
Resource for clinicians to help confirm diagnosis; American College of Medical Genetics.
Services for Patients & Families Nationwide (NW)
Service Categories | # of providers* in: | NW | Partner states (5) (show) | | NM | NV | OH | RI | UT | |
---|---|---|---|---|---|---|---|---|---|---|
Biochemical Genetics (Metabolics) | 1 | 1 | 2 | 1 | 3 | 3 | ||||
Developmental - Behavioral Pediatrics | 1 | 2 | 2 | 2 | 12 | 9 | ||||
Genetic Testing and Counseling | 4 | 4 | 11 | 5 | 6 | 11 | ||||
Nutrition, Metabolic | 13 | 13 | 15 | 14 | 15 | 14 | ||||
Pediatric Neurology | 5 | 5 | 17 | 7 |
For services not listed above, browse our Services categories or search our database.
* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.
Studies
MCADD (ClinicalTrials.gov)
Studies looking at better understanding, diagnosing, and treating this condition; from the National Library of Medicine.
Helpful Articles
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Medium-Chain Acyl-CoA Dehydrogenase Deficiency: Evaluation of Genotype-Phenotype Correlation in Patients Detected by Newborn
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The clinical manifestation of MCAD deficiency: challenges towards adulthood in the screened population.
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PubMed abstract
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Dobbelaere D, Briand G, Jeannesson E, Vassault A, Vianey-Saban C.
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Arch Pediatr.
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PubMed abstract
Authors & Reviewers
Author: | Brian J. Shayota, MD, MPH |
2016: update: Laurie Smith, MD, Ph.D.SA; Natario Couser, MD, MSR |
2010: update: Laurie Smith, MD, Ph.D.A |
2008: first version: Holly WelshCA |
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