MASS phenotype

MASS phenotype

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:

  • 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.

MASS phenotype is (mitral valve prolapse, myopia, borderline and nonprogressive aortic enlargement, and nonspecific skin and skeletal findings

  • Autosomal dominant condition affecting connective tissue that presents with several features in common with Marfan syndrome; rarely, can be caused by heterozygous FBN1 gene variants 
  • Common manifestations of disease that overlap with those of Marfan syndrome include mitral valve prolapse, myopia, borderline nonprogressive aortic dilation, similar skeletal manifestations (eg, scoliosis, chest wall deformities, joint hypermobility), and similar skin manifestations (eg, striae atrophicae )
  • Diagnosis is difficult to discriminate from emerging Marfan syndrome; therefore, it is usually established in patients aged 20 years or older 
  • Differentiate from Marfan syndrome by clinical manifestations and course of disease (eg, nonprogressive nature of aortic dilation, absence of ectopia lentis) 
  • Definitive diagnosis is established in patients aged 20 years or older whose condition does not fulfill Ghent criteria for Marfan syndrome and who have the following:
    • Aortic root z score less than 2
    • Negative family history of Marfan syndrome
    • Systemic score of 5 or more with presence of at least 1 skeletal feature
    • Absence of development of ectopia lentis
  • Presence of family history with concordant manifestations confirms the diagnosis


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