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PubMed This is a summary of 9 peer-reviewed journal articles Updated
Medical Genetics

The Biology and Genetics of CMAMMA

At a Glance

CMAMMA is a metabolic condition caused by variations in the ACSF3 gene. This genetic change reduces the mitochondria's ability to process malonic acid, leading to a buildup of malonic and methylmalonic acids. Unlike classic MMA, CMAMMA carries a much lower metabolic risk.

To understand Combined Malonic and Methylmalonic Acidemia (CMAMMA), it helps to look inside the mitochondria—the “power plants” of your cells [1]. CMAMMA is caused by a glitch in the body’s instruction manual for a specific mitochondrial worker called the ACSF3 enzyme [2].

The ACSF3 Gene and Its Enzyme

The ACSF3 gene provides the code to build an enzyme called malonyl-CoA synthetase (MCS) [1]. Think of this enzyme as a specialized technician in the mitochondria whose job is to “activate” malonic acid by turning it into a molecule called malonyl-CoA [3][1].

When the ACSF3 gene has mutations (variations), this technician cannot do its job effectively. This leads to two main problems:

  1. Acid Buildup: Because malonic acid isn’t being converted, it “backs up” in the system like a clogged pipe, leading to high levels of both malonic acid (MA) and methylmalonic acid (MMA) in the blood and urine [1][2].
  2. Energy Shortage: The mitochondria lose a key ingredient they need to function at 100% efficiency [4].

Energy Synthesis and “Spark Plugs”

The “activated” malonic acid created by ACSF3 is a vital building block that the mitochondria need to make energy [4].

In simple terms, this pathway helps create an essential “spark plug” (called lipoic acid) for several other major enzymes [1].

  • The Chain Reaction: When ACSF3 doesn’t work, production decreases, and the “spark plugs” aren’t available for other energy-producing enzymes [1][4].
  • The Result: The cell’s ability to create energy is slightly impaired, which is why some people with CMAMMA might experience neurological or developmental symptoms [4][5].

How CMAMMA Differs from Classic MMA

It is very common for CMAMMA to be confused with Classic Methylmalonic Acidemia (MMA) because they share similar names and both involve elevated MMA. However, they happen in different “rooms” of the mitochondrial factory:

Feature CMAMMA Classic MMA
Faulty Enzyme Malonyl-CoA synthetase (ACSF3) [1] Methylmalonyl-CoA mutase (MUT) [6]
Primary Goal Processing malonic acid for energy synthesis [1] Breaking down proteins and certain fats [7]
Urine Findings High Malonic and Methylmalonic acid [8] High Methylmalonic acid only [8]
Metabolic Risk Low; usually stable [9] High; risk of life-threatening crisis [9]

In CMAMMA, the buildup of methylmalonic acid (MMA) is actually a “byproduct” of the ACSF3 enzyme not working, rather than a failure to break down protein [1]. This is why the medical management for CMAMMA is typically much less restrictive than for classic MMA [9].

Common questions in this guide

What causes CMAMMA?
CMAMMA is caused by variations or mutations in the ACSF3 gene. This gene provides the instructions for making a mitochondrial enzyme called malonyl-CoA synthetase, which helps process malonic acid.
How does the ACSF3 mutation affect mitochondrial energy production?
The ACSF3 mutation prevents the mitochondria from creating a crucial spark plug needed for several energy-producing enzymes. Because of this missing link, the cell's ability to create energy is slightly impaired, which can lead to fatigue or neurological symptoms.
Why does a problem with malonic acid processing also cause methylmalonic acid to build up?
When the ACSF3 enzyme is not working properly, malonic acid cannot be processed and backs up in the system like a clogged pipe. The elevated methylmalonic acid happens as a secondary byproduct of this primary failure to process malonic acid.
What is the difference between CMAMMA and classic MMA?
While both conditions involve high methylmalonic acid, they occur in different parts of the mitochondrial factory. Classic MMA involves a failure to break down proteins and carries a high risk of metabolic crisis, whereas CMAMMA is typically stable and carries low metabolic risk.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.How does the ACSF3 mutation specifically change the way my (or my child's) mitochondria produce energy?
  2. 2.Why does a problem with malonic acid processing also cause methylmalonic acid to build up?
  3. 3.Can you explain my plasma MA/MMA ratio and how it rules out classic methylmalonic acidemia?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (9)
  1. 1

    A Deep Clinical and Biochemical Characterization of a Patient With Combined Malonic and Methylmalonic Aciduria (CMAMMA).

    Gragnaniello V, Galderisi A, Tucci S, et al.

    JIMD reports 2025; (66(6)):e70045 doi:10.1002/jmd2.70045.

    PMID: 41030468
  2. 2

    Biallelic ACSF3 variants with combined malonic and methylmalonic acidemia and associated developmental epileptic encephalopathy phenotype: A novel genotype-phenotype correlation.

    Curry J, Bonkowski E, Mefford H, et al.

    Seizure 2025; (133()):16-19 doi:10.1016/j.seizure.2025.09.015.

    PMID: 41075375
  3. 3

    Dual molecular genetic diagnosis with combined malonic and methylmalonic aciduria (CMAMMA): implications of coexisting genetic disorders on clinical presentation.

    Ersoy M, Abali ZY, Papatya Cakir ED, et al.

    Journal of pediatric endocrinology & metabolism : JPEM 2025; (38(12)):1340-1349 doi:10.1515/jpem-2025-0208.

    PMID: 40960910
  4. 4

    The emerging role of the mitochondrial fatty-acid synthase (mtFASII) in the regulation of energy metabolism.

    Wehbe Z, Behringer S, Alatibi K, et al.

    Biochimica et biophysica acta. Molecular and cell biology of lipids 2019; (1864(11)):1629-1643 doi:10.1016/j.bbalip.2019.07.012.

    PMID: 31376476
  5. 5

    Brain metabolism and neurological symptoms in combined malonic and methylmalonic aciduria.

    Tucci S

    Orphanet journal of rare diseases 2020; (15(1)):27 doi:10.1186/s13023-020-1299-7.

    PMID: 31969167
  6. 6

    [MOLECULAR-GENETIC ASPECTS OF METHYLMALONIC ACIDURIA DEVELOPMENT (REVIEW)].

    Zharmakhanova G, Syrlybayeva L, Kononets V, et al.

    Georgian medical news 2021; 118-124.

    PMID: 34103442
  7. 7

    A novel small molecule approach for the treatment of propionic and methylmalonic acidemias.

    Armstrong AJ, Collado MS, Henke BR, et al.

    Molecular genetics and metabolism 2021; (133(1)):71-82 doi:10.1016/j.ymgme.2021.03.001.

    PMID: 33741272
  8. 8

    A New Approach for Fast Metabolic Diagnostics in CMAMMA.

    de Sain-van der Velden MG, van der Ham M, Jans JJ, et al.

    JIMD reports 2016; (30()):15-22 doi:10.1007/8904_2016_531.

    PMID: 26915364
  9. 9

    Combined Malonic and Methylmalonic Aciduria Due to ACSF3 Variants Results in Benign Clinical Course in Three Chinese Patients.

    Wang P, Shu J, Gu C, et al.

    Frontiers in pediatrics 2021; (9()):751895 doi:10.3389/fped.2021.751895.

    PMID: 34900860

This page explains the biology and genetics of CMAMMA for educational purposes only. Always consult your geneticist or metabolic specialist for medical advice regarding your specific diagnosis and test results.

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