What are the other Names for this Condition? (Also known as/Synonyms)

• SD1 (Syndactyly Type 1)
• SDTY1 (Syndactyly Type 1)
• Zygodactyly

What is Syndactyly Type 1? (Definition/Background Information)

• Syndactyly Type 1 is a congenital limb developmental defect that involves webbing or joining of the fingers or toes. Syndactyly type 1 is the most common type of non-syndromic syndactyly
• Individuals with syndactyly type 1 have webbing of the third and fourth fingers and/or between the second and third toes. Other digits may be involved, as well as the underlying bones
• There are four different subtypes of syndactyly type 1, differentiated by slightly different hand and foot symptoms
• Syndactyly type 1 may be inherited in an autosomal dominant manner and is suspected to be caused by a gene mutation on the long (q) arm of chromosome 2 between 2q34 and 2q36
• Treatment usually involves surgery to separate the digits

(Source: Syndactyly Type 1; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

Who gets Syndactyly Type 1? (Age and Sex Distribution)

• Syndactyly Type 1 is a rare congenital disorder, with an estimated annual occurrence of 2-3/10,000 among newborns
• The condition can affect both males and females
• Worldwide, individuals of all races and ethnicities may be born with this disorder

What are the Risk Factors for Syndactyly Type 1? (Predisposing Factors)

• A positive family history may be an important risk factor, since Syndactyly Type 1 can be inherited
• Currently, no other risk factors have been clearly identified for Syndactyly Type 1

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Syndactyly Type 1? (Etiology)

• The exact gene mutation that causes Syndactyly Type 1 is not known at the present time
• The locus of the causative gene has been determined to be the long arm of chromosome 2, between loci 2q32 and 2q34
• The disorder is inherited in an autosomal dominant manner

Autosomal dominant inheritance: Autosomal dominant conditions are traits or disorders that are present when only one copy of the mutation is inherited on a non-sex chromosome. In these types of conditions, the individual has one normal copy and one mutant copy of the gene. The abnormal gene dominates, masking the effects of the correctly function gene. If an individual has an autosomal dominant condition, the chance of passing the abnormal gene on to their offspring is 50%. Children, who do not inherit the abnormal gene, will not develop the condition or pass it on to their offspring.

What are the Signs and Symptoms of Syndactyly Type 1?

The signs and symptoms of Syndactyly Type 1 may include:

• 2-3 toe syndactyly
• 3-4 finger syndactyly
• Distal symphalangism of hands

Based on the frequency of symptoms observed, the following information may be noted:

Very frequently present symptoms in 80-99% of the cases:

• Finger syndactyly
• Toe syndactyly

Occasionally present symptoms in 5-29% of the cases:

• Sagittal craniosynostosis
• Symphalangism affecting the phalanges of the hand

(Source: Syndactyly Type 1; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

How is Syndactyly Type 1 Diagnosed?

Syndactyly Type 1 is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Syndactyly Type 1?

The complications of Syndactyly Type 1 may include:

• Difficulty in grasping and lifting objects
• Failure of surgery to result in stable, functional and mobile fingers
• Abnormal shape of head
• Low self-esteem

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Syndactyly Type 1 Treated?

There is no cure for Syndactyly Type 1, since it is a genetic condition.

• The treatment is usually given to manage the signs and symptoms and any complication that develops
• This may be achieved by surgical separation of the joined fingers and/or toes
• The separation of fused fingers and toes may require multiple surgeries, if the fusion is not limited to the soft tissue, but involves the bones

How can Syndactyly Type 1 be Prevented?

Syndactyly Type 1 may not be preventable, since it is a genetic disorder.

• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Syndactyly Type 1? (Outcomes/Resolutions)

• The prognosis of Syndactyly Type 1 is dependent upon the severity of the signs and symptoms and associated complications, if any
• In some cases, surgical separation of the joined fingers/toes may not result in fully functional digits. It may compromise the function of the affected individual’s hands and/or feet

Additional and Relevant Useful Information for Syndactyly Type 1:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/