Greig cephalopolysyndactyly syndrome is a genetic disorder that affects development of the limbs, head, and face.

Mutations in the GLI3 gene cause Greig cephalopolysyndactyly syndrome. The GLI3 gene provides instructions for making a protein that controls gene expression, which is a process that regulates whether genes are turned on or off in particular cells. By interacting with certain genes at specific times during development, the GLI3 protein plays a role in the normal shaping of many organs and tissues before birth.

This condition is very rare; its prevalence is unknown. This condition is inherited in an autosomal dominant pattern, which means one altered or missing copy of the GLI3 gene in each cell is sufficient to cause the disorder. In some cases, an affected person inherits a gene mutation or chromosomal abnormality from one affected parent. Other cases occur in people with no history of the condition in their family.

The features of this syndrome are highly variable, ranging from very mild to severe. People with this condition may have:

• One or more extra fingers or toes (polydactyly)
• An abnormally wide thumb or big toe (hallux)
• The skin between the fingers and toes may be fused (cutaneous syndactyly)
• Widely spaced eyes (ocular hypertelorism)
• An abnormally large head size (macrocephaly)
• A high, prominent forehead

Rarely, affected individuals may have more serious medical problems including:

• Seizures
• Developmental delay
• Intellectual disability

Treatment consists of correcting and monitoring the syndrome’s manifestations, including:

• Elective surgical repair of polydactyly with greatest priority given to correction of preaxial polydactyly of the thumbs
• Evaluation and treatment as needed for water on the brain (hydrocephalus) or other abnormalities in individuals showing signs of increased intracranial pressure, developmental delay, loss of milestones, and/or seizures.
• Monitoring for evidence of head circumference increasing faster than normal.