This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
MASS phenotype is a familial connective tissue disorder similar to Marfan syndrome that affects different people in different ways. MASS is an acronym for features of the disorder that may be present:
People with MASS phenotype also have nearsightedness (myopia), but they do not experience eye lens dislocation (ectopia lentis) as in Marfan syndrome.
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. 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. It may be hard to distinguish MASS phenotype from early features of Marfan syndrome in young individuals.
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.
For more information, visit GARD.