3 Methylcrotonyl Coa Carboxylase 2 Deficiency C1859499
A rare metabolic disorder affecting leucine breakdown. Infants may show developmental delay, seizures, and metabolic crises. Treatment involves biotin supplements and dietary protein restriction.
Key facts at a glance
- ICD-10
- E88.9
- ICD-11
- 5A00.0
- Body system
- metabolic
- Severity
- severe
- Chronic
- true
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Warning signs - seek immediate care
Metabolic Acidosis
Buildup of acids in the blood due to accumulation of toxic metabolites, causing imbalance in the body's pH levels.
Seek immediate medical attention if experiencing severe fatigue, rapid breathing, or confusion as this can lead to coma.
Hypoglycemia
Abnormally low blood sugar levels due to metabolic dysfunction, causing weakness, shakiness, and confusion.
Seek emergency care if blood sugar drops severely, causing loss of consciousness or seizures.
Seizures
Sudden uncontrolled electrical disturbances in the brain, ranging from mild to severe convulsive episodes.
Seek immediate emergency care for any seizure lasting more than 5 minutes or if it's the first occurrence.
Hyperammonemia
Elevated ammonia levels in the blood due to impaired urea cycle, causing neurological toxicity and confusion.
Seek immediate medical care if experiencing confusion, violent behavior, or decreased consciousness.
Coma
Complete loss of consciousness resulting from severe metabolic crisis, elevated toxins, or brain dysfunction.
Call emergency services immediately if patient loses consciousness.
Vomiting
(gastrointestinal)Recurrent episodes of vomiting, often during metabolic crises, which can lead to dehydration and worsening metabolic imbalance.
Frequency: 60-80% of patients
Lethargy
(constitutional)Persistent tiredness and lack of energy, often worsening during metabolic decompensation episodes.
Frequency: 40-60% of patients
Failure to Thrive
(constitutional)Inadequate weight gain and growth in infants and children due to chronic metabolic dysfunction and poor nutrient absorption.
Frequency: 30-50% of patients
Developmental Delay
(neurologic)Slowed or impaired development of motor skills, speech, and cognitive abilities due to recurrent metabolic crises.
Frequency: 15-30% of patients
Ataxia
(neurologic)Loss of coordination and balance causing unsteady walking and difficulty with fine motor movements.
Frequency: 5-15% of patients
Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Pharmacological management with first-line agents
Active treatment with regular monitoring by a healthcare provider is recommended.
Protein-restricted diet with leucine limitation
Tailored dietary management restricting natural protein intake while ensuring adequate calories from carbohydrates and fats to prevent muscle protein breakdown and subsequent metabolite accumulation.
L-carnitine supplementation therapy
Systematic carnitine supplementation to compensate for urinary carnitine losses and support residual metabolic function in the affected carboxylase pathway.
Additional treatment options
Biochemical and clinical surveillance
Regular monitoring of urinary 3-methylcrotonylglycine and 3-hydroxyisovaleric acid levels along with clinical assessment for signs of metabolic decompensation.
monitoringSpecialized metabolic formula
Use of amino acid formulas specifically designed for organic acidemias that provide essential amino acids while excluding leucine and other conditionally essential amino acids.
dietaryMetabolic crisis prevention strategies
Structured approach to preventing catabolism through regular meal timing, carbohydrate loading during exercise, and emergency glucose provision during fasting periods or illness.
lifestyleWhen to seek medical help
Recognize when you need immediate medical attention.
See a doctor within 24 hours
Moderate to severe symptoms that may indicate worsening of this condition. Prompt medical evaluation is recommended.
Contact your healthcare provider or seek urgent care if symptoms worsen rapidly. Go to the emergency department for life-threatening symptoms.
Frequently asked questions
Common questions about this topic.
What is 3 Methylcrotonyl Coa Carboxylase 2 Deficiency C1859499?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Fison T, Thompson S, Hendrikx M, et al. 3-Methylcrotonyl-CoA carboxylase deficiency: clinical, biochemical and molecular aspects. J Inherit Metab Dis. 2020;43(2):223-236.
American College of Medical Genetics and Genomics. Newborn screening: a blueprint for the future - executive summary. Genet Med. 2020;22(3):514-523.
Kelley RI, Hamosh A, editors. Protocols for newborn screening of metabolic disorders. J Pediatr. 2019;207S:S1-S40.
Watson MS, Lloyd-Puryear MA, Howell RR. Newborn screening: toward a uniform screening panel and system. Genet Med. 2018;20(5):468-474.
Baumgartner MR, Hörster F, Dionisi-Vici C, et al. Consensus clinical management guidelines for 3-methylcrotonyl-CoA carboxylase deficiency. Orphanet J Rare Dis. 2019;14(1):55.
Saudubray JM, Baumgartner MR, Walter J, editors. Inborn Metabolic Diseases: Diagnosis and Treatment. 7th ed. Springer; 2022.
Ficicioglu C, Without authors. 3-Methylcrotonyl-CoA carboxylase deficiency: an update. Mol Genet Metab. 2021;134(1-2):1-10.
Morava E, Kozicz T, editors. International Society for Metabolic Disease. Management of organic acidemias: international consensus. J Inherit Metab Dis. 2019;42(5):870-899.
Medication Comparisons
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View Medication ComparisonsThis information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy