In general terms, most doctors use neonatal Marfan syndrome to describe children who have striking outward characteristics at the time of birth, as well as significant cardiovascular (heart) involvement in very early infancy.
Particularly pronounced features often include long extremities and fingers, joint laxity and contractures, a characteristic facial appearance with deeply set and downward slanting eyes and/or crumpled ears, loose and redundant skin, poor feeding, breathing difficulties, enlarged cornea or glaucoma, and severe prolapse and leakage through the mitral and/or tricuspid heart valves that can lead to poor squeeze of the heart muscle (heart failure).
Other findings typical of milder forms of Marfan syndrome can also be present including pectus deformity (indented or protruding chest), scoliosis (curved back), nearsightedness, aortic root dilatation (enlargement), and eye lens dislocation.
Neonatal Marfan syndrome is the worst end of the spectrum and, even within the neonatal Marfan patients, there is a range in severity, depending on the combination of features and the severity of the individual components.
Neonatal Marfan syndrome is a different entity than Marfan syndrome. It has early onset and rapidly progressive features, most seriously related to the heart, lungs, and airways.
Many doctors use neonatal Marfan syndrome to describe the severe end of the clinical spectrum of Marfan syndrome, rather than considering this a discrete clinical entity. Care should be taken to avoid use of this designation simply because a child is diagnosed with Marfan syndrome in early infancy, as this might simply relate to an early evaluation due to a family history of Marfan syndrome or a particularly astute pediatrician, as opposed to atypically severe disease severity.