Answer:
Elastic fibers are made of elastin and microfibrils, that are elastic protein structures. The proteins can be stretched and resume normal shape. These fibers are found in parts of the body such as arteries, skin, lungs, connective tissue and heart that require some stretching. Marfan syndrome affects the elastic connective tissues causing symptoms like dilation of the aorta that doesn't resume normal lumen diameter (aortic aneurysm), and curving of the spine (scoliosis).
The lungs are unable to stretch and resume shape normally and this affects the respiratory system. The subjects will suffer from shortness of breath, wheezing and chest pain.
The sheath/endoneurium of neurons is connective tissue. This part of a neuron allows signals to travel effeciently along the axon of the neuron. This means that a person with Mafran syndrome has a slower response to stimuli that ordinary persons.