Disease at a Glance

Ring chromosome 18 is a rare chromosome abnormality in which the ends (arms) of chromosome 18 join together to form a ring shape. When a ring chromosome forms, genetic material can be lost from either arm or both arms, causing various signs and symptoms. While most people with Ring chromosome 18 have the ring chromosome in all of their body cells, some people also have some body cells with normal chromosomes (this is called mosaicism). People with Ring chromosome 18 mosaicism may have milder symptoms. Depending on the amount of genetic material lost and which genes are involved, signs and symptoms that may be present in a person with Ring chromosome 18 include ear and hearing abnormalities, abnormally-developed feet or hands, genital abnormalities in males, an increased risk to develop juvenile rheumatoid arthritis, holoprosencephaly, developmental delays, learning difficulties, short stature, and/or various birth defects. Ring chromosome 18 usually occurs sporadically (by chance) during the formation of egg or sperm cells or shortly after the egg and sperm join together. Occasionally, it is inherited from a parent (typically the mother). A chromosome test of the parents can help determine whether it was inherited and whether future children have an increased chance to have a chromosome abnormality.
Estimated Number of People with this Disease
In the U.S. there may be between

1 to 300

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?
The most common ages for symptoms of a disease to begin is called age of onset. Age of onset can vary for different diseases and may be used by a doctor to determine the diagnosis. For some diseases, symptoms may begin in a single age range or several age ranges. For other diseases, symptoms may begin any time during a person's life.
Prenatal Selected
Before Birth
Newborn Selected
Birth-4 weeks
Infant Selected
1-23 months
2-11 years
12-18 years
19-65 years
Older Adult
65+ years
The common ages for symptoms to begin in this disease are shown above by the colored icon(s).


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