Sequencing the entire gene for mutations is tedious, and often detects mutations that may represent normal variation, resulting in both false positives and false negatives. Immunohistological evaluation of skin for abnormal fibrillin has been reported but is not widely available. For now, diagnosis of Marfan syndrome remains a clinical one. Others, however, are more subtle in their presentation and require years of close follow-up to diagnose. Detailed diagnostic criteria are now available.
Diagnosis is based on manifestations in tissue and organ systems as well as family history.
A series of major and minor criteria is used. Mitral valve prolapse, dilatation of the main pulmonary artery without valvular or peripheral pulmonic stenosis or other obvious cause before 40 years, or dilatation or dissection of the descending aorta before 50 years. Spontaneous pneumothorax and apical blebs. If a mutation known to cause Marfan syndrome is present in other family members, major criterion in one organ system and involvement of another organ system. Common Medical Complications Cardiovascular abnormalities are the principle cause of mortality in Marfan syndrome.