Brachydactyly type E

Alternate names

Type E brachydactyly

Definition

Brachydactyly type E is a genetic disorder that causes some of the bones of the hands or feet to be shorter than expected.

Forms

• Brachydactyly type E can be isolated or syndromic.
• If the disorder is isolated, it means that the person does not have any other health problems or symptoms related to having brachydactyly type E.
• If brachydactyly type E is syndromic, it means a person has another genetic disease or health issue that includes the shortening of the hand and feet bones as one of its symptoms.

Cause

• Brachydactyly type E can be isolated or syndromic.
• Syndromic means there are other physical differences or health problems present due to the same genetic change. In these cases, there may be an underlying genetic syndrome that is causing the shortened hands and feet and other health problems.
• When brachydactyly type E is isolated, meaning a person has shortened bones in the hands and feet but no other physical differences or related health problems, it may be caused by genetic changes (pathogenic variants or mutations) in HOXD13 gene. Pathogenic variants in the the PTHLH gene can also cause brachydactyly type E.
• Changes in this gene are also usually associated with short height and in some cases learning disabilities and problems with teeth.
• Both of these genes provide instructions for proteins that help control bone growth.
• It is thought that there may be other genes in which pathogenic variants cause isolated brachydactyly type E with or without short stature.
• This is because some people with isolated brachydactyly type E with or without short stature do not have pathogenic variants in the PTHLH or HOXD13 genes.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

When caused by pathogenic variants in the PTHLH or HOXD13 gene, brachydactyly type E is inherited in an autosomal dominant manner. Like most genes, the PTHLH or HOXD13 genes come in a pair (two copies of each gene). One copy of the genes is inherited from each parent. When a syndrome is inherited in an autosomal dominant manner, a person must have a pathogenic variant in only one copy of the gene to have the disorder. When a person with a pathogenic variants in either the PTHLH or HOXD13 gene has children, for each child there is a:

• 50% chance to inherit the change in the PTHLH or HOXD13 gene, meaning the child will have brachydactyly type E
• 50% chance to inherit the working copy of the PTHLH or HOXD13 gene, meaning the child will not have brachydactyly type E

If a person has brachydactyly type E and other related physical or health problems, the underlying genetic syndrome may be inherited in a different pattern.

Signs and symptoms

• Brachydactyly type E causes some of the bones of the hands or feet to be shorter than expected, which causes the hands and feet to appear small. Specifically, the bones that are shortened in people with brachydactyly type E are the metacarpals (bones in the hands) and metatarsals (bones in the feet).
• In some cases, the long bones of the fingers or toes (phalanges) may also be shortened.
• Other signs and symptoms of brachydactyly type E may include having very flexible joints in the hands (hyperextensibility), having a round face, and being shorter than expected (short stature).
• Depending on the genetic cause other symptoms may be present, including learning disabilities and problems with teeth.
• The shortening of the bones in the hands and feet in people with brachydactyly type E may be noticed shortly after birth, however the difference often becomes more obvious as people get older.
• The number of metacarpals and metatarsals that are smaller than normal can range from a few of the bones to all of the bones, even within the same family. When the symptoms of a disorder vary even with the same genetic change, the disorder is said to have variable expressivity.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Short metacarpal(Shortened long bone of hand)
• Type E brachydactyly

30%-79% of people have these symptoms

• Joint hyperflexibility(Joints move beyond expected range of motion)
• Short distal phalanx of finger(Short outermost finger bone)
• Short stature(Decreased body height)

5%-29% of people have these symptoms

• Aplasia/Hypoplasia of the distal phalanx of the hallux(Absent/small outermost big toe bone)
• Frontal bossing
• Macrocephaly(Increased size of skull)
• Short metatarsal(Short long bone of foot)
• Upper limb asymmetry(Unequal size of arms)

Diagnosis

• Brachydactyly type E may be diagnosed when a doctor finds that a baby, child, or adult has shorter hands and feet than expected and also has very flexible (hyperextensible) joints in the hands.
• In some cases, a doctor may order x-rays of the hands and feet to confirm the diagnosis.
• A doctor may also take a thorough medical and family history and perform a physical exam and other tests to determine if there are any other health problems or physical differences that may be related to a genetic syndrome.
• In some cases, genetic testing may be used to confirm if the disorder is isolated or associated with another genetic syndrome.

Treatment

• There is no specific management or treatment that is applicable to all forms of brachydactyly.
• Plastic surgery is only indicated if the brachydactyly affects hand function or for cosmetic reasons, but is typically not needed.
• Physical therapy and ergotherapy may ameliorate hand function.

Prognosis

• Most people who only have brachydactyly type E without any other health or physical problems do not find their quality of life affected very much by having smaller hands and feet, as long as they have full use of their hands and feet.
• If brachydactyly type E is caused by an underlying genetic syndrome, the long-term outlook can vary depending on the underlying syndrome.

NIH genetic and rare disease info

• NIH info on Brachydactyly type E

Brachydactyly type E is a rare disease.

Brachydactyly type E Resources
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