How to Check the Marfan Syndrome Thumb & Wrist Signs

When evaluating for Marfan syndrome, doctors often check for two physical indicators known as the Steinberg (thumb) sign and the Walker-Murdoch (wrist) sign. These are quick, simple physical tests that help identify if a person has unusually long, slender fingers and loose joints ^[1][2]. While these tests are iconic features of Marfan syndrome, testing positive for one or both does not automatically mean you have the condition ^[3].

The Steinberg (Thumb) Sign

The Steinberg sign evaluates finger length and joint flexibility.

• How to check: Hold your hand out flat. Fold your thumb across your palm, and then close your other four fingers over the thumb to make a fist.
• A positive sign: The test is positive if the entire tip of your thumb (distal phalanx), including the thumbnail, sticks out visibly beyond the far edge (the pinky side) of your palm ^[4].

The Walker-Murdoch (Wrist) Sign

The Walker-Murdoch sign also checks for long bones and joint flexibility, specifically in the wrist and fingers.

• How to check: Use your thumb and pinky (little finger) to wrap around the narrowest part of your opposite wrist.
• A positive sign: The test is positive if the tips of your thumb and pinky overlap each other while gripping the wrist ^[4].

What Do These Signs Indicate?

If you have a positive thumb or wrist sign, it usually points to a combination of two physical traits ^[1]:

• Arachnodactyly (long bone overgrowth): A medical term that means fingers are disproportionately long and slender compared to the rest of the hand or body ^[5].
• Joint hypermobility: Often called “loose joints,” this means the ligaments that hold your joints together are more relaxed, allowing the joints to stretch further than usual ^[1]. Children naturally have looser joints, so false positives can be particularly common in youth.

Because Marfan syndrome is a disorder of the body’s connective tissue, people with the condition frequently display both of these traits ^[2].

Why Positive Signs Don’t Mean a Diagnosis

It is crucial to understand that having a positive thumb or wrist sign does not mean you have Marfan syndrome ^[1][3]. These physical features can be found in people with other connective tissue conditions (such as Ehlers-Danlos syndrome), in people with a naturally slender build, or in people who just happen to be double-jointed ^[1][3]. Conversely, it is entirely possible to have Marfan syndrome even if you do not display these specific signs.

Doctors use a checklist called the Revised Ghent Nosology to diagnose Marfan syndrome ^[6][4]. In this scoring system:

• Having only one of the signs gives you 1 point.
• Having both a positive thumb and wrist sign gives you 3 points ^[4].
• A score of 7 or higher is needed just to meet the “systemic” (whole body) criteria for the condition ^[4].

A definitive diagnosis relies heavily on more significant signs that cannot be seen on the outside of the body, particularly an enlarged aorta (aortic root aneurysm) or a dislocated lens in the eye (ectopia lentis) ^[4]. If you notice these thumb and wrist signs in yourself or a family member, it is simply a piece of information to discuss with your doctor rather than a reason to panic.