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Disease Profile

MASS phenotype

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Overlap connective tissue disease; OCTD; MASS syndrome


MASS phenotype is a familial connective tissue disorder similar to Marfan syndrome that affects different people in different ways.[1] MASS is an acronym for features of the disorder that may be present:[1][2][3]

  • Mitral valve prolapse a heart condition in which the two valve flaps of the mitral valve in the heart do not close smoothly or evenly, and bulge (prolapse) upward into the left atrium.
  • Aortic root dilation borderline, non-progressive enlargement of the section of the aorta where the aorta and heart meet. Unlike in Marfan syndrome, aortic complications such as dissection and aneurysm usually do not occur. However some authors believe there may be an increased risk for aortic complications.
  • Skin striae (stretch marks) skin may have stretch marks even without changes in weight.
  • Skeletal features possible features include curvature of the spine (scoliosis), chest wall deformities, and joint hypermobility.

People with MASS phenotype also have nearsightedness (myopia), but they do not experience eye lens dislocation (ectopia lentis) as in Marfan syndrome.[1]

MASS phenotype has rarely been diagnosed in people with a mutation in the FBN1 gene (which usually causes Marfan syndrome), but in most cases the cause of MASS phenotype is not yet known.[3][4] People diagnosed with MASS phenotype who do have a FBN1 mutation may later be diagnosed with Marfan syndrome as additional features develop, which would convey a high risk of aortic complications.[3] It may be hard to distinguish MASS phenotype from early features of Marfan syndrome in young individuals.[2]

Management focuses on the specific symptoms and severity in each person. It is important to monitor signs and symptoms over time, such as having annual heart and eye exams. This is especially important for people under 20 years of age who potentially have Marfan syndrome, since additional features may develop with age.[5]


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
Percent of people who have these symptoms is not available through HPO
Abnormal sternum morphology
Abnormality of the sternum
Sternal anomalies

[ more ]

Aortic aneurysm
Bulge in wall of large artery that carries blood away from heart
Autosomal dominant inheritance
Disproportionate tall stature
Mitral valve prolapse
Striae distensae
Stretch marks


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      In-Depth Information

      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss MASS phenotype. Click on the link to view a sample search on this topic.


        1. MASS Phenotype. The Marfan Foundation. https://www.marfan.org/mass-phenotype. Accessed 8/29/2018.
        2. Wright MJ, Connolly, HM. Genetics, clinical features, and diagnosis of Marfan syndrome and related disorders. UpToDate. Waltham, MA: UpToDate; November 2, 2016; https://www.uptodate.com/contents/genetics-clinical-features-and-diagnosis-of-marfan-syndrome-and-related-disorders.
        3. Rippe M, De Backer J, Kutsche K. et al. Mitral valve prolapse syndrome and MASS phenotype: Stability of aortic dilatation but progression of mitral valve prolapse. Int J Cardiol Heart Vasc. January 21, 2016; 10:39-46. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441352/.
        4. Defendi GL. Genetics of Marfan Syndrome. Medscape Reference. January 4, 2017; https://emedicine.medscape.com/article/946315-differential.
        5. Wright MJ, Connolly, HM. Management of Marfan syndrome and related disorders. Unique. Waltham, MA: UpToDate; April 3, 2018; https://www.uptodate.com/contents/management-of-marfan-syndrome-and-related-disorders.