Bone overgrowth in the head causes many of the signs and symptoms of craniometaphyseal dysplasia. Affected individuals typically have distinctive facial features such as a wide nasal bridge, a prominent forehead, wide-set eyes (hypertelorism), and a prominent jaw. Excessive new bone formation (hyperostosis) in the jaw can delay teething (dentition) or result in absent teeth. Infants with this condition may have breathing or feeding problems caused by narrow nasal passages. In severe cases, abnormal bone growth can compress the nerves that emerge from the brain and extend to various areas of the head and neck (cranial nerves). Compression of the cranial nerves can lead to paralyzed facial muscles (facial nerve palsy), blindness, or deafness.
The x-rays of individuals with craniometaphyseal dysplasia show unusually shaped long bones, particularly the large bones in the legs. The ends of these bones (metaphyses) are wider and appear less dense in people with this condition.
The symptoms seen in autosomal recessive craniometaphyseal dysplasia are typically more severe than those seen in the autosomal dominant form.
The Human Phenotype Ontology (HPO) provides the following list of features that have been reported in people with this condition. Much of the information in the HPO comes from Orphanet, a European rare disease database. If available, the list includes a rough estimate of how common a feature is (its frequency). Frequencies are based on a specific study and may not be representative of all studies. You can use the MedlinePlus Medical Dictionary for definitions of the terms below.
|Signs and Symptoms||Approximate number of patients (when available)|
|Abnormality of the metaphyses||90%|
|Depressed nasal bridge||90%|
|Increased bone mineral density||90%|
|Wide nasal bridge||90%|
|Conductive hearing impairment||7.5%|
|Sensorineural hearing impairment||7.5%|
|Abnormality of pelvic girdle bone morphology||-|
|Abnormality of the nasopharynx||-|
|Abnormality of the vertebral column||-|
|Autosomal dominant inheritance||-|
|Bony paranasal bossing||-|
|Club-shaped distal femur||-|
|Erlenmeyer flask deformity of the femurs||-|
|Misalignment of teeth||-|
|Mixed hearing impairment||-|
|Sclerosis of skull base||-|
Autosomal dominant craniometaphyseal dysplasia is caused by mutations in the 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.
Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.
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My niece has been diagnosed with autosomal dominant craniometaphyseal dysplasia. Can you provide information regarding treatment and research ? See answer