Lincoln did not have Marfan syndrome. People with Marfan have long thin fingers and tend to be weaker than normal. Lincoln displayed great strength, for example in wood-chopping demonstrations, and once during the Civil War, when he held a very heavy ax at arms length by the end of the handle. Also casts of Lincoln’s hands survive, which show his hands to be very strong and not like those of someone with Marfan syndrome.
Lincoln was also know to be an accomplished wrestler in his youth. It is very unlikely someone with Marfan’s would excel at wrestling.
My friends daughter with Marfans was born with webbed fingers and toes and she is recovering from heart transplant surgery. I have only seen the girl once but her face and neck are very strange, like she has too many tendons connecting them. She has had dozens of surgeries to correct problems with the connective tissue all over her body.