Oral-facial-digital syndrome is actually a group of related conditions that affect the development of the oral cavity (the mouth and teeth), facial features, and digits (fingers and toes).

Researchers have identified at least 13 potential forms of oral-facial-digital syndrome. The different types are classified by their patterns of signs and symptoms. However, the features of the various types overlap significantly, and some types are not well defined. The classification system for oral-facial-digital syndrome continues to evolve as researchers find more affected individuals and learn more about this disorder.

The signs and symptoms of oral-facial-digital syndrome vary widely. However, most forms of this disorder involve problems with development of the oral cavity, facial features, and digits. Most forms are also associated with brain abnormalities and some degree of intellectual disability.

Abnormalities of the oral cavity that occur in many types of oral-facial-digital syndrome include a split (cleft) in the tongue, a tongue with an unusual lobed shape, and the growth of noncancerous tumors or nodules on the tongue. Affected individuals may also have extra, missing, or defective teeth. Another common feature is an opening in the roof of the mouth (a cleft palate). Some people with oral-facial-digital syndrome have bands of extra tissue (called hyperplastic frenula) that abnormally attach the lip to the gums.

Distinctive facial features often associated with oral-facial-digital syndrome include a split in the lip (a cleft lip); a wide nose with a broad, flat nasal bridge; and widely spaced eyes (hypertelorism).

Abnormalities of the digits can affect both the fingers and the toes in people with oral-facial-digital syndrome. These abnormalities include fusion of certain fingers or toes (syndactyly), digits that are shorter than usual (brachydactyly), or digits that are unusually curved (clinodactyly). The presence of extra digits (polydactyly) is also seen in most forms of oral-facial-digital syndrome.

Other features occur in only one or a few types of oral-facial digital syndrome. These features help distinguish the different forms of the disorder. For example, the most common form of oral-facial-digital syndrome, type I, is associated with polycystic kidney disease. This kidney disease is characterized by the growth of fluid-filled sacs (cysts) that interfere with the kidneys' ability to filter waste products from the blood. Other forms of oral-facial-digital syndrome are characterized by neurological problems, particular changes in the structure of the brain, bone abnormalities, vision loss, and heart defects.

Only one gene, OFD1, has been associated with oral-facial-digital syndrome. Mutations in this gene cause oral-facial-digital syndrome type I. OFD1 gene mutations were also found in an affected family whose disorder was classified as type VII; however, researchers now believe that type VII is the same as type I.

The OFD1 gene provides instructions for making a protein whose function is not fully understood. It appears to play an important role in the early development of many parts of the body, including the brain, face, limbs, and kidneys. Mutations in the OFD1 gene prevent cells from making enough functional OFD1 protein, which disrupts the normal development of these structures. It is unclear how a shortage of this protein causes the specific features of oral-facial-digital syndrome type I.

Researchers are actively searching for the genetic changes responsible for the other forms of oral-facial-digital syndrome.

Normal Function

The OFD1 gene provides instructions for making a protein whose function is not fully understood. It appears to play a critical role in the early development of many parts of the body, including the brain, face, limbs, and kidneys.

The OFD1 protein is located at the base of cilia, which are finger-like projections that stick out from the surface of cells. Cilia are involved in cell movement and in many different chemical signaling pathways. They play important roles in the development and function of many parts of the body. Researchers suspect that the OFD1 protein is essential for the normal formation of cilia.

Studies suggest that the OFD1 protein may have additional functions. In the earliest stages of development, it appears to be involved in determining the left-right axis (the imaginary line that separates the left and right sides of the body). The OFD1 protein is also found in the nucleus, although its function in this cell structure is unknown.

Health Conditions Related to Genetic Changes

Oral-facial-digital syndrome

About 100 mutations in the OFD1 gene have been found in people with oral-facial-digital syndrome type I, which is the most common form of the disorder. These mutations include changes in single DNA building blocks (base pairs) and larger deletions of genetic material from the OFD1 gene. Most of these genetic changes lead to the production of an abnormally short, nonfunctional version of the OFD1 protein. It is unclear how a shortage of functional OFD1 protein leads to the specific features of oral-facial-digital syndrome type I. However, studies suggest that a lack of this protein prevents the normal formation of cilia, which affects the development of many tissues and organs.

Joubert syndrome

Mutations in the OFD1 gene can also cause several other disorders with features that overlap with those of oral-facial-digital syndrome (described above), such as Joubert syndrome. This disorder is characterized by particular brain abnormalities, weak muscle tone (hypotonia), delayed development, unusual eye movements, and breathing problems.

The OFD1 mutations responsible for Joubert syndrome lead to the production of an abnormally short version of the OFD1 protein. However, studies suggest that these mutations result in a somewhat longer protein than the mutations that cause oral-facial-digital syndrome. This protein may retain some of its usual function in cilia. The abnormal protein probably disrupts the development or function of cilia in some way, although it is unclear how these changes result in the signs and symptoms of Joubert syndrome.

Primary ciliary dyskinesia

MedlinePlus Genetics provides information about Primary ciliary dyskinesia

Simpson-Golabi-Behmel syndrome

MedlinePlus Genetics provides information about Simpson-Golabi-Behmel syndrome

Other disorders

At least one OFD1 gene mutation has been found in a family with a form of X-linked intellectual disability. Individuals with this condition have severe intellectual disability, an unusually large head size (macrocephaly), and breathing problems.

This OFD1 gene mutation leads to the production of an abnormally short version of the OFD1 protein. However, the altered protein appears to be longer than the abnormal proteins involved in oral-facial-digital syndrome (described above). This protein may retain some of its usual function in cilia. The abnormal protein probably disrupts the development or function of cilia in some way, although it is unclear how these changes result in the signs and symptoms of X-linked intellectual disability.

Other Names for This Gene

• 71-7A
• CXorf5
• JBTS10
• MGC117039
• MGC117040
• OFD1_HUMAN
• oral-facial-digital syndrome 1
• SGBS2

Genomic Location

Oral-facial-digital syndrome type I is inherited in an X-linked dominant pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In females (who have two X chromosomes), a mutation in one of the two copies of the gene in each cell is sufficient to cause the disorder. Some cells produce a normal amount of OFD1 protein and other cells produce none. The resulting overall reduction in the amount of this protein leads to the signs and symptoms of oral-facial-digital syndrome type I.

In males (who have only one X chromosome), mutations result in a total loss of the OFD1 protein. A lack of this protein is usually lethal very early in development, so very few males are born with oral-facial-digital syndrome type I. Affected males usually die before birth, although a few have lived into early infancy.

Most of the other forms of oral-facial-digital syndrome are inherited in an autosomal recessive pattern, which suggests that both copies of a causative gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Oral-facial-digital syndrome has an estimated incidence of 1 in 50,000 to 250,000 newborns. Type I accounts for the majority of cases of this disorder. The other forms of oral-facial-digital syndrome are very rare; most have been identified in only one or a few families.