KIF7 Gene

Acrocallosal syndrome is a rare condition characterized by a brain abnormality called agenesis of the corpus callosum, the presence of extra fingers and toes (polydactyly), and distinctive facial features. The signs and symptoms of this disorder are present at birth, and their severity varies widely among affected individuals.

Agenesis of the corpus callosum occurs when the tissue that connects the left and right halves of the brain (the corpus callosum) fails to form normally during the early stages of development before birth. Other brain abnormalities, including the growth of large cysts in brain tissue, have also been reported in people with acrocallosal syndrome. The changes in brain structure associated with this condition lead to delayed development and intellectual disability, which is most often moderate to severe. Some affected individuals also experience seizures.

Extra fingers and toes are common in people with acrocallosal syndrome. The extra digits can be on the same side of the hand or foot as the pinky or little toe (postaxial polydactyly) or on the same side as the thumb or great toe (preaxial polydactyly). Some affected individuals also have webbed or fused skin between the fingers or toes (syndactyly).

Distinctive facial features that can occur with acrocallosal syndrome include widely spaced eyes (hypertelorism) and a high, prominent forehead. Many affected individuals also have an unusually large head size (macrocephaly).

Joubert syndrome is a disorder that affects many parts of the body. The signs and symptoms of this condition vary among affected individuals, even among members of the same family.

The hallmark feature of Joubert syndrome is a combination of brain abnormalities that together are known as the molar tooth sign, which can be seen on brain imaging studies such as magnetic resonance imaging (MRI). This sign results from the abnormal development of structures near the back of the brain, including the cerebellar vermis and the brainstem. The molar tooth sign got its name because the characteristic brain abnormalities resemble the cross-section of a molar tooth when seen on an MRI.

Most infants with Joubert syndrome have low muscle tone (hypotonia) in infancy, which contributes to difficulty coordinating movements (ataxia) in early childhood. Other characteristic features of the condition include episodes of unusually fast (hyperpnea) or slow (apnea) breathing in infancy, and abnormal eye movements (ocular motor apraxia). Most affected individuals have delayed development and intellectual disability, which can range from mild to severe. Distinctive facial features can also occur in Joubert syndrome; these include a broad forehead, arched eyebrows, droopy eyelids (ptosis), widely spaced eyes (hypertelorism), low-set ears, and a triangle-shaped mouth.

Joubert syndrome can include a broad range of additional signs and symptoms. The condition is sometimes associated with other eye abnormalities (such as retinal dystrophy, which can cause vision loss, and coloboma, which is a gap or split in a structure of the eye), kidney disease (including polycystic kidney disease and nephronophthisis), liver disease, skeletal abnormalities (such as the presence of extra fingers and toes), or hormone (endocrine) problems. A combination of the characteristic features of Joubert syndrome and one or more of these additional signs and symptoms once characterized several separate disorders. Together, those disorders were referred to as Joubert syndrome and related disorders (JSRD). Now, however, any instances that involve the molar tooth sign, including those with these additional signs and symptoms, are usually considered Joubert syndrome.