Disease at a Glance

Methylmalonic acidemia with homocystinuria is an inherited disorder in which the body is unable to properly process certain nutrients from food including amino acids, lipids and cholesterol. People with this disorder have a combination of features from two separate conditions: methylmalonic acidemia and homocystinuria. When the condition begins early in life, babies have difficulty gaining weight (failure to thrive), feeding difficulties, and a pale appearance. Babies may also have weak muscle tone (hypotonia) and seizures. Most babies and children with this condition have an unusually small head size (microcephaly), intellectual disability and developmental delay. Less common features of the condition include eye problems and a blood disorder called megaloblastic anemia. When the disorder begins in adolescence or adulthood, the signs and symptoms usually include behavior and personality changes and cognitive problems (issues with learning, memory, perception etc). In some cases, abilities are lost, resulting in a decline of performance, memory and speech problems, dementia and lethargy.[12470 Methylmalonic acidemia with homocystinuria can be caused by genetic changes in one of several genes: MMACHC, MMADHC, LMBRD1, ABCD4, or HCFC1. Genetic changes in these genes account for the different types of the disorder, cblC, cblD, cblF, cblJ, and cblX, respectively.
Estimated Number of People with this Disease

This section is currently in development.

What Information Does GARD Have For This Disease?

Many rare diseases have limited information. Currently GARD is able to provide the following information for this disease:

*Data may be currently unavailable to GARD at this time.
When do symptoms of this disease begin?
This section is currently in development. 


This section is currently in development. We recommend speaking with a doctor to learn more about this disease. 


This section is currently in development. 

Next Steps

Talking with the Medical Team

Good communication between the patient, family, and medical team can lead to an accurate diagnosis. In addition, health care decisions can be made together which improves the patient’s well-being and quality of life.

Describing Symptoms

Describe details about the symptoms. Because there may be many different causes for a single symptom, it is best not to make a conclusion about the diagnosis. The detailed descriptions help the medical provider determine the correct diagnosis.

To help describe a symptom:

  • Use a smartphone or a notebook to record each symptom before the appointment
  • Describe each symptom by answering the following questions:
    • When did the symptom start?
    • How often does it happen?
    • Does anything make it better or worse?
  • Tell the medical team whether any symptoms affect daily activities

Preparing for the First Visit

Working with a medical team to find a diagnosis can be a long process that will require more than one appointment. Make better health decisions by being prepared for the first visit with each member of the medical team.

    Make informed decisions about health care: 
    • Prepare a list of questions and concerns before the appointment
    • List the most important questions first, not all questions may be answered in the first visit
    • Ask questions about symptoms, possible diagnoses, tests, and treatment options
    For future appointments:
    • Discuss what was not addressed at the last visit
    • Discuss changes in the quality of life for the patient, family, and caregivers
    • Discuss health goals and other issues in the patient’s and family’s life that may affect the health care decisions
    Take notes during the appointments to help remember what was discussed.

    Last Updated: Nov. 8, 2021