Is there a marfan's-like syndrome that is linked to autism?

Possibly: Homcystinuria is an inherited metabolic disorder that worsens with age, has psychiatric symptoms and may appear to be similar to autism. Homocystinuria can mimic marfan's syndrome, since most patients with MS are tall and lanky and have visual and extremity problems. If your doctor is suspicious they will check for this. See http://www.Ncbi.Nlm.Nih.Gov/pubmedhealth/pmh0002179/.

Not that I know: The only likely association i can think is klinefelter's sydrome. But this is not close. Ks is only in males, they tend to be taller than average (similar to marfan's) and may have motor delays and learning problems (similar to autism) . But they usually lack the main features of profound communication and social skills impairment of as. Many/most klindefelter's appear entirely normal.

? Klinefelter's: You may be thinking of something called linefelter's syndrome, a chromosomal disorder with some behavioral and physical characteristics that put the two referenced in mind.