Clinically, another disease, inherited, has almost similar features of Marfan's syndrome . It is known as homocystinuria . But there are dissimilarities too.

inheritance:

Marfan's - autosomal dominant
homocystinuria - autosomal recessive

lens dislocation:

Marfan's - upward lens dislocation
homocystinuria - downward lens dislocation

aortic incompetence:

Marfan's - aortic incompetence may occur
homocystinuria - heart rarely affected

intellectual development:

Marfan's - normal
homocystinuria - mental retardation

other principle features:

Marfan's - flat feet, herniae, scoliosis; there is a 50% reduction in life expectancy
homocystinuria - osteoporosis, recurrent thromboembolism; characteristic laboratory features - plasma methionine and homocystine levels are elevated, homocystine is excreted in the urine, plasma cystine levels are reduced, positive urine cyanide-nitroprusside test; response to treatment with pyridoxine
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