Brachydactyly is a congenital condition, meaning you're born with it. When you have it, your fingers and toes are much shorter than average compared to the size of your body.
There are many types of brachydactyly, which affect your fingers and toes in different ways. While it affects the way your feet and hands look, for most people, brachydactyly doesn't affect how well they work.
What Causes Brachydactyly?
Is brachydactyly genetic?
Most types of brachydactyly are genetic. A single gene change (mutation) can affect how bones grow before birth. You can inherit brachydactyly even if just one of your parents has the mutation that causes it. If you have brachydactyly, other family members may have it too.
In many cases, brachydactyly doesn't involve any other health problems; you simply have shorter fingers or toes. You may not even know that you have brachydactyly unless you get a hand or foot X-ray for another condition.
What else causes brachydactyly?
Medications. Sometimes, brachydactyly happens when you take certain drugs during pregnancy. For example, anticonvulsant medications used to treat epilepsy or other conditions may raise the risk that your baby will be born with short fingers or toes. Poor blood flow in the baby during development can also lead to brachydactyly.
Syndromes. Brachydactyly also appears as part of some broader genetic syndromes and medical conditions, including:
- Brachydactyly-mesomelia-intellectual disability-heart defects syndrome
- Apert syndrome
- Down syndrome
- Robinow syndrome
- Rubinstein-Taybi syndrome
- Turner’s syndrome
- Albright's hereditary osteodystrophy
- Cushing's syndrome
- Genetic conditions that involve short stature, such as acrodysostosis or pseudohypoparathyroidism
What Are the Types of Brachydactyly?
Because it can be caused by mutations in several genes, brachydactyly appears in five forms. Each form involves a different gene and affects different fingers or toes.
Type A brachydactyly
This form affects the middle bones of your fingers. It includes three subtypes:
Type A1. This type shortens the middle bone of all fingers. It's linked to mutations in the IHH gene.
Type A2. This affects the middle bone of your index finger, and sometimes your little finger. It's linked to mutations in the BMPR1B or GDF5 genes.
Type A3. With this type, only the middle bone of your little finger is shortened. It's tied to mutations in the HOXD13 gene.
Type B brachydactyly
This type of brachydactyly affects bones in the tips of your fingers and/or toes. The bones may be shorter than normal or missing. Your thumbs and big toes aren't affected. This type is linked to changes in the ROR2 gene.
Type C brachydactyly
This rare type affects three fingers on each hand. Your index, middle, and little fingers have shorter middle bones, so your ring finger becomes the longest. Changes in the GDF5 gene cause this type.
Type D brachydactyly
This is the most common form of brachydactyly. This type shortens the final bone in your thumb but doesn't affect the fingers. It's linked to changes in the HOXD13 gene.
Type E brachydactyly
This is the rarest form of brachydactyly. It's most often part of another condition that you're born with. Type E causes short thumbs and big toes. This type is linked to changes in the HOXD13 or PTHLH genes.
How Does Brachydactyly Impact Your Health?
Brachydactyly rarely affects your overall health. Only in extreme cases will brachydactyly make it difficult to do tasks. Otherwise, it affects your health only if you have it along with another health condition.
In some children, it helps doctors spot another condition that may affect growth or hormone levels.
How to Prevent Brachydactyly From Affecting Your Health
Brachydactyly doesn't usually cause pain or health problems. Sometimes, it can be a little inconvenient, such as when you're trying to find shoes or gloves that fit well. And your hands and feet will look a little different from other people's. But overall, it doesn't get in the way of everyday life.
If you have brachydactyly along with another health issue, the other problem is usually what will affect your life the most.
In rare, serious cases of brachydactyly, your doctor may recommend physical therapy. This usually happens when the condition is serious enough to make walking or gripping things difficult. In those situations, therapy can help improve movement, strength, and function in your fingers or toes.
FAQs About Brachydactyly
Why is brachydactyly type D called murderer's thumb?
People call brachydactyly type D the "murderer's thumb" because of an old myth. A long time ago, people, especially palm readers and fortune tellers, thought that a short, thick thumb with a wide nail meant someone had a bad temper or violent nature, but there's no truth to that. It's just a name that has persisted due to old superstitions.
What syndrome is associated with brachydactyly?
Brachydactyly can show up on its own or as part of a genetic condition. Some examples include:
- Down syndrome
- Turner's syndrome
- Robinow syndrome
- Apert syndrome
- Rubinstein-Taybi syndrome
- Cushing's syndrome
- Albright's hereditary osteodystrophy
In these cases, short fingers or toes are part of a bigger pattern of symptoms that affect different parts of the body.
What is a type 3 brachydactyly?
Type 3 brachydactyly, also called type A3, affects the pinky finger and sometimes other fingers. The middle bone is smaller than usual.