Mass Phenotype | The Marfan Foundation

Mass Phenotype

What is MASS Phenotype?

MASS Phenotype is a connective tissue disorder that is similar to Marfan syndrome. It is caused by a similar mutation in the gene called fibrillin-1 that tells the body how to make an important protein found in connective tissue.  Someone with MASS phenotype has a 50 percent chance of passing the gene along to each child.

People with features of MASS Phenotype need to see a doctor who knows about connective tissue disorders for an accurate diagnosis; often this will be a medical geneticist. It is very important that people with MASS Phenotype get an early and correct diagnosis so they can get the right treatment.

MASS stands for the Mitral valve, myopia, Aorta, Skin and Skeletal features of the disorder. MASS Phenotype affects different people in different ways.

In MASS Phenotype:

  • Mitral valve prolapse may be present. This is when the flaps of one of the heart’s valves (the mitral valve, which regulates blood flow on the left side of the heart) are “floppy” and don’t close tightly.
  • Aortic root diameter may be at the upper limits of normal for body size, but unlike Marfan syndrome there is not progression to aneurysm or predisposition to dissection.
  • Skin may show stretch marks unrelated to weight gain or loss (striae).
  • Skeletal features, including curvature of the spine (scoliosis), chest wall deformities, and joint hypermobility, may be present.

People with MASS Phenotype do not have lens dislocation but have myopia, also known as nearsightedness.

To learn more about MASS Phenotype and its diagnosis and treatment, download:

MASS phenotype