Thumb/wrist sign

Positive when the thumb protrudes from the clenched fist, in which the other four digits are flexed over the thumb.
 

Patient 1:

This is a young man with Marfan’s syndrome.

This patient also has a large wing span.

Patient 2:

This patient has Marfan’s syndrome.

Patient 3:

This is a young man with Marfan’s syndrome. Note the arachnodactyly, high-arched palate (ogival palate), thumb sign, wrist sign, and wide wing span.