← All diseases

Inborn errors of metabolism

Methylmalonic acidemia (MMA)

An inherited metabolic disease. The body cannot fully break down certain proteins and fats. Acid builds up in the blood; vomiting, weakness and developmental problems can occur.

Not part of the panel of Türkiye's National Newborn Screening Programme (heel-prick test). Source

Prepare an emergency card

This page is translated from the Turkish original.

This disease is followed through the “Inborn errors of metabolism” group.

Understanding the disease

This section has not yet been reviewed by a physician. It summarises patient information from sources such as MedlinePlus, Orphanet and the NHS in plain language. The disease can differ from person to person; talk to your doctor about diagnosis and treatment.

What happens in this disease?

An enzyme, or the vitamin B12 system it needs to work, is faulty. As a result, some protein building blocks and fats cannot be fully broken down. Methylmalonic acid and other harmful substances build up. The blood becomes acidic and organs can be damaged.

Which symptoms can occur?

Symptoms usually begin in early infancy. They range from mild to severe. Infection or too much protein can trigger episodes.

  • Vomiting and loss of fluids
  • Weakness and excessive sleepiness
  • Floppy muscles
  • Poor weight gain and slow growth
  • Enlarged liver
  • Developmental delay
  • In the long term, kidney disease and inflammation of the pancreas
  • Movement disorders

How is it diagnosed?

In many countries, it can be found through expanded newborn screening. Methylmalonic acid and related substances are measured in the blood and urine. The diagnosis is confirmed with a genetic test; brain imaging may also be done.

Treatment and care

The basis of care is a special diet that restricts certain proteins, and a special formula. Eating often and regularly is important. Some forms respond to vitamin treatment. Some children need additional nutritional supplements. During an episode, treatment in hospital may be needed. New treatments are being researched. The doctor who follows the disease decides which treatment is suitable.

For the family: inheritance and genetic counselling

The disease is passed on through recessive inheritance. The mother and father are usually healthy carriers. For a couple who are both carriers, the chance of having an affected child is 1 in 4 in each pregnancy. When relatives marry, the chance that two carriers have children together is higher. Genetic counselling guides the family.

Source: MedlinePlus Genetics: Methylmalonic acidemia · NORD: Methylmalonic Acidemia

Key facts

How common is it?
Prevalence: 1-9 per 100 000 (Europe)
When does it usually start?
Any age

These facts are taken from Orphanet and MedlinePlus records (last checked: October 7, 2026). Frequency values are approximate ranges.

You are not alone: patient associations in Türkiye

Non-profit patient and family organizations in Türkiye working on this disease or disease group. Links are for information; Doktorclub is not affiliated with these organizations and does not endorse them.

For all rare diseases: Nadir Hastalıklar Federasyonu

Links checked on October 8, 2026.

Guides related to this disease

  • Special diets and medical nutrition · Metabolic diet, blood monitoring, medical formula and SGK report, sick-day plan, tube feeding and swallowing problems, school meals, supplement warning
  • Rare disease at school · Telling the school, medicines and emergency plan, inclusion and BEP, support education room, absences, LGS/YKS arrangements, peer bullying.

Support and help

Doktorclub does not diagnose, recommend treatments or refer you to hospitals or doctors. These pages are meant to help you talk with your doctor.

News about MMA

Clinical trials (ClinicalTrials.gov)

A clinical trial is a regulated study that tests whether a new treatment is safe and whether it works, in patients who volunteer. Most trials look for a certain age, genetic change and health condition. Taking part is voluntary.

This list is not a treatment recommendation. Treatments tested in phase 1–3 trials are investigational (experimental): their efficacy and safety have not yet been proven and they are not approved treatments. Taking part depends on each trial’s criteria and a physician’s assessment; the first step is to talk to the doctor who manages your care.

Questions you can ask your doctor

  • Could this trial be suitable for us?
  • If we take part, how would current treatment and check-ups be affected?
  • Where does the trial take place, and how are travel and accommodation handled?
  • What happens if we want to leave the trial?

ClinicalTrials.gov lists 3 active interventional studies for this disease. 1 is recruiting now; none has a site in Türkiye. Last checked: October 7, 2026.

Selected records (studies with a site in Türkiye first):

See all studies on ClinicalTrials.gov · Joining clinical trials

Inborn errors of metabolism: other news

Medical codes (for talking with your doctor and finding sources)

These codes identify the disease in international classifications and databases. They can help when you talk with your doctor or look for reliable sources.

Orphanet code: ORPHA:293355

No matching ICD-11 entry was found.

Codes checked against WHO ICD-11 and Orphanet on October 7, 2026.

This page provides general information and does not replace diagnosis or treatment. Talk to your doctor about symptoms, diagnosis and treatment.

The information on these pages is for general information only and does not replace medical advice. Talk to your doctor about diagnosis and treatment decisions. In an emergency in Türkiye, call 112.

Every update is based on an open source and labeled with its level of evidence. No advertising and no drug brand names. Our scientific principles

This page was translated from Turkish by the Doktorclub editorial team.