Split hand foot malformation

Split hand foot malformation (SHFM) is a type of birth defect that consists of missing digits (fingers and/or toes), a deep cleft down the center of the hand or foot, and fusion of remaining digits.^[1][2] The severity of this condition varies widely among affected individuals. SHFM is sometimes called ectrodactyly; however, this is a nonspecific term used to describe missing digits.^[3] SHFM may occur by itself (isolated) or it may be part of a syndrome with abnormalities in other parts of the body. At least six different forms of isolated SHFM have been described. Each type is associated with a different underlying genetic cause. SHFM1 has been linked to chromosome 7, and SHFM2 is linked to the X chromosome. SHFM3 is caused by a duplication of chromosome 10 at position 10q24. Changes (mutations) in the TP63 gene cause SHFM4. SHFM5 is linked to chromosome 2, and SHFM6 is caused by mutations in the WNT10B gene. SHFM may be inherited in an autosomal dominant, autosomal recessive, or X-linked manner.

Split hand foot malformation may occur as an isolated feature or it may be associated with a genetic syndrome. Researchers believe that a large number of mutations can cause split hand foot malformation. A few of which have been identified: FBXW4 and TP63. Most commonly the conditions are passed through families in an autosomal dominant fashion with reduced penetrance. In autosomal dominant inheritance an affected parent would have a 1 in 2 or 50% chance with each pregnancy of passing the genetic defect to his/her offspring. In conditions with “reduced penetrance” a person who inherits the underlying genetic defect, may never develop the condition.^[2]

More rarely other forms of inheritance have been reported (e.g., autosomal-recessive, X-linked, chromosome deletions, chromosome duplications).^[2]

The chance that a child would inherit split hand foot malformation from a parent with this condition, depends on the type of split hand foot malformation in the parent and its underlying cause. Most cases of isolated split hand foot malformation are inherited in an autosomal dominant manner. Other forms of inheritance is possible. To learn more about your specific risks we recommend that you speak with a genetics professional.

Today there are a number of genetic tests that can be used to inform a couple about the possible outcomes of a current or future pregnancy. Examples of two such tests are prenatal diagnosis and preimplantation genetic diagnosis (PGD). Prenatal diagnosis can be used to diagnose a condition in a developing fetus. Today, doctors are able to diagnose many more birth defects than they are able to treat before birth. If a fetus has a condition for which prenatal treatment is not possible, prenatal diagnosis may help parents prepare emotionally for the birth and to plan the delivery with their health care providers.^[4] Parents can also use this information to make decisions regarding whether or not to continue the pregnancy. 

PGD represents an alternative to prenatal diagnosis.^[5] It is used following in vitro fertilization to diagnose a genetic disease or condition in embryos. Only embryos that do not carry the disease-causing mutation are implanted in the mother's womb. PGD allows testing to occur before a pregnancy begins.

In many cases, the disease-causing mutation must be identified in an affected relative before PGD or prenatal diagnosis can be performed.

You can learn more about these and other tests by visiting the links below to the view information on this topic developed by the Centre for Genetic Education and by the Genetics and Public Policy Center:
http://www.genetics.com.au/pntbooklet.pdf
http://www.dnapolicy.org/policy.issue.php?action=detail&issuebrief_id=7

Couples considering these options should talk with their healthcare provider and a genetic professional. It is important that couples are fully informed of the risks and benefits of each testing option and also have an opportunity to explore their feelings and beliefs regarding the use of these technologies. More information about genetic consultations is available from Genetics Home Reference at http://ghr.nlm.nih.gov/handbook/consult. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:  

• GeneTests has a searchable directory of US and international genetics and prenatal diagnosis clinics.
• The National Society for Genetic Counselors provides a searchable directory of US and international genetic counseling services.
• The American College of Medical Genetics has a searchable database of US genetics clinics.
• The University of Kansas Medical Center provides a list of US and international genetic centers, clinics, and departments.
• The American Society of Human Genetics maintains a database of its members, which includes individuals who live outside of the United States. Visit the link to obtain a list of the geneticists in your country, some of whom may be researchers that do not provide medical care.

No appropriate nonoperative treatment is available for split hand foot malformation, and prostheses have been largely abandoned except on occasions when they are requested for cosmetic purposes. The operative management must be individualized. In general, good pinch and grasp are the primary goals of surgery, followed by acceptable cosmetic appearance if possible. In planning the sequence and timing of surgery, patients should speak with their doctor and surgeon regarding their surgical options.^[6]