Autosomal dominant craniometaphyseal dysplasia is a genetic skeletal condition characterized by progressive thickening of bones in the skull (cranium) and abnormalities at the ends of long bones in the limbs (metaphyseal dysplasia). The overgrowth of bones in the head can lead to distinctive facial features and delayed tooth eruption, as well as compression of the cranial nerves. If untreated, compression of the cranial nerves can be disabling. The condition is caused by mutations in the ANKH gene. As the name suggests, it is inherited in an autosomal dominant manner. Treatment may include surgery to reduce compression of cranial nerves and recontouring of the facial bones.

ANKH gene. The ANKH gene provides instructions for making a protein that is present in bone and transports a molecule called pyrophosphate out of cells. Pyrophosphate helps regulate bone formation by preventing mineralization, the process by which minerals such as calcium and phosphorus are deposited in developing bones. The ANKH protein may have other, unknown functions.Mutations in the ANKH gene that cause autosomal dominant craniometaphyseal dysplasia may decrease the ANKH protein's ability to transport pyrophosphate out of cells. Reduced levels of pyrophosphate can increase bone mineralization, contributing to the bone overgrowth seen in craniometaphyseal dysplasia. Why long bones are shaped differently and only the skull bones become thicker in people with this condition remains unclear.

ANKH gene in each cell is sufficient to cause the disorder. Individuals with autosomal dominant craniometaphyseal dysplasia typically have one parent who also has the condition. Less often, cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

The symptoms seen in autosomal recessive craniometaphyseal dysplasia are typically more severe than those seen in the autosomal dominant form.

Treatment consists primarily of surgery to reduce compression of cranial nerves and the brain stem/spinal cord at the level of the foramen magnum. Severely overgrown facial bones can be contoured; however, surgical procedures can be technically difficult and bone regrowth is common. Individuals with craniometaphyseal dysplasia should have regular neurologic evaluations, hearing assessments, and ophthalmologic examinations. The frequency of these evaluations and assessments should be determined by the individual's history and severity of skeletal changes.