Arachnodactyly

Arachnodactyly describe the appearance of long fingers and long limbs. The name implies
the resemblance to a spider. In the limbs there is a reduced upper to lower segment ratio.

Arachnodactyly is often seen in Marfan's syndrome.

There are ways of quantifying arachnodactyly if its presence is in question:

• the thumb sign is said to be positive if the thumb protrudes the palm when flexed across
  it


• the wrist sign is said to be positive if the thumb and fifth fingers overlap when they
  encircle the opposite wrist

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