Hyperostosis Frontalis Interna is characterized by the thickening of the frontal bone of the skull. It is not clear that this disorder is actually rare. Some clinicians believe that it may be a common abnormality found in as many as 12 percent of the female population. The disorder may be found associated with a variety of conditions such as seizures, headaches, obesity, diabetes insipidus, excessive hair growth and sex gland disturbances. Increased serum alkaline phosphatase and elevated serum calcium may occur.
The major feature of Hyperostosis Frontalis Interna is excessive growth or thickening of the frontal bone of the head. This excess growth can only be seen in an x-ray. As a result, scientists feel that this condition may be much more prevalent than suspected, but often goes undetected. Many people have no apparent symptoms.
Other conditions that may be found in patients with this disorder are: obesity, a condition in which secondary male sexual traits are acquired by a female (virilization); a central nervous system disorder characterized by a sudden, aimless, uncontrollable discharge of electrical energy in the brain causing a convulsion or loss of consciousness (epilepsy); decreased vision; headaches; disturbances of the ovaries and testes (sex glands or gonads); excessive body hair; and/or diabetes. (For more information on these disorders, choose “Epilepsy” and/or “Diabetes” as your search terms in the Rare Disease Database).
Hyperostosis Frontalis Interna has been found in multiple generations suggesting that the disorder may be inherited as a dominant trait. It is not known if the disorder is autosomal dominant or X-linked. There are no known cases of male-to-male (father to son) transmission.
Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
Hyperostosis Frontalis Interna affects females 9 times more often than males. This disorder presents itself most often among the middle-aged and elderly but has also been found in adolescents.
There is no known treatment for Hyperostosis Frontalis Interna. Seizures and headaches can be treated with standard medications.
Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.
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FROM THE INTERNET
McKusick, VA. ed. On-line Mendelian Inheritance in Man (OMOM); Entry: 144800, Hyperostosis Frontalis Interna. Creation Date: 6/4/1986. Most recent update: 9/24/94.