Maxillofacial Dysostosis

Disease Overview

Maxillofacial dysostosis is an extremely rare genetic disorder characterized by distinctive abnormalities of the head and face (craniofacial) area. Major symptoms include an underdeveloped (hypoplasia) upper jaw, downward-slanting palpebral fissures (which means that the opening between the eyelids slants downward), minor malformations of the external portion of the ears, and speech abnormalities. Maxillofacial dysostosis is inherited as an autosomal dominant trait. A second (distinct) form of maxillofacial dysostosis is believed to be inherited as an X-linked recessive trait.

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Synonyms

autosomal dominant maxillofacial dysostosis

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Signs & Symptoms

The symptoms and physical findings associated with maxillofacial dysostosis may vary from one person to another. Because so few cases have been identified and reported, it will be difficult to obtain an accurate clinical picture of the disorder. Affected individuals or parents of affected children should talk to their physicians and medical team about their specific case and associated symptoms.

Characteristic findings associated with maxillofacial dysostosis include an underdeveloped (hypoplastic) upper jaw (maxilla), an abnormal downward slant of the opening between the eyelids (palpebral fissures), minor external ear malformations and speech abnormalities.

Although most individuals with maxillofacial dysostosis have normal intelligence, they are often mistakenly thought to be mentally challenged due to their language problems. Their progress should be carefully monitored and educators should be informed of the potential for delayed onset of speech and difficulties with speech development including poor speech articulation (dysarthria).

External ear abnormalities may include malformation of the upper, outer portion of the ear (pinna or auricle). Hearing loss was not seen in any of the individuals with maxillofacial dysostosis reported in the medical literature. Additional symptoms that have been reported in some cases of maxillofacial dysostosis include a sunken chest (pectus excavatum), incomplete or underdeveloped nipples, an abnormally flat skull, and a flattened bridge of the nose. Certain eye abnormalities including drooping of the upper eyelid (ptosis), crossed eyes (strabismus), and rapid, involuntary movements of the eyes (nystagmus) have also been reported.

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Causes

Maxillofacial dysostosis is inherited as an autosomal dominant trait. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.

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Affected populations

Maxillofacial dysostosis is extremely rare and the exact incidence of the disorder is unknown. Approximately 12 cases have been reported in the medical literature. Researchers believe that cases of maxillofacial dysostosis may go misdiagnosed or unrecognized making it difficult to determine the true frequency of the disorder in the general population. Maxillofacial dysostosis most likely affects males and females in equal numbers.

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Disorders with Similar Symptoms

Symptoms of the following disorders can be similar to those of maxillofacial dysostosis. Comparisons may be useful for a differential diagnosis.

X-linked maxillofacial dysostosis, sometimes referred to as Toriello syndrome, is a rare genetic disorder characterized by an abnormally small jaw (micrognathia), underdevelopment of the middle portion of the face (midface hypoplasia), ear abnormalities, and an abnormal downward slant of the opening between the eyelids (palpebral fissures). Additional symptoms include short stature, cognitive impairment, a slightly webbed neck and hearing loss. The disorder is believed to be inherited as an X-linked recessive trait.

Nager syndrome (also known as mandibulofacial dysostosis) is a rare inherited disorder characterized by craniofacial malformations similar to those in Treacher Collins syndrome occurring in association with abnormalities of the arms, hands, and/or feet. Craniofacial malformations include underdevelopment of the cheekbones (malar hypoplasia); incomplete development of the lower jaw (mandibular hypoplasia), causing the jaw to appear abnormally small (micrognathia); hypoplastic and/or malformed (dysplastic) external ears (pinnae) and blind ending or absent external ear canals (microtia), resulting in hearing impairment (conductive hearing loss); and/or downwardly slanted palpebral fissures, lack or absence of the lower eyelashes, and/or drooping upper eyelids (ptosis). Limb abnormalities include underdevelopment or absence of the thumbs, absence of one of the bones in the forearms (radius), abnormal fusion of bones in the forearms (radioulnar synostotis), permanent flexion of certain fingers (camptodactyly), and/or webbing of the toes (syndactyly). In most cases, Nager syndrome appears to occur randomly, for no apparent reason (sporadic). In other cases, researchers suggest that the disorder may be inherited as an autosomal dominant or recessive trait. (For more information on this disorder, choose “Nager” as your search term in the Rare Disease Database.)

Treacher Collins syndrome is a rare genetic disorder characterized by distinctive abnormalities of the craniofacial area due to underdevelopment (hypoplasia) of certain bones of the head including the cheekbones and nearby structures (zygomatic complex and the jaw. The specific symptoms and physical characteristics associated with Treacher Collins syndrome may vary greatly from case to case. Craniofacial abnormalities tend to involve the cheekbones, jaws, mouth, ears, and/or eyes. In addition to the various facial abnormalities, affected individuals may have malformations of the external ears and middle ear structures and eye (ocular) abnormalities including an abnormal downward slant to the opening between the upper and lower eyelids (palpebral fissures). Affected individuals may develop hearing loss and breathing (respiratory) difficulties. In some cases, affected individuals may have mild symptoms and may go undiagnosed. In approximately 40 percent of cases, Treacher Collins syndrome has autosomal dominant inheritance. However, in about 60 percent of cases, a positive family history is not found. These cases likely represent new genetic changes (mutations) that occur randomly, with no apparent cause (sporadic). (For more information on this disorder, choose “Treacher Collins” as your search term in the Rare Disease Database.)

Acrodysostosis is an extremely rare skeletal disorder characterized by abnormally short and malformed bones of the hands and feet (peripheral dysostosis) and underdevelopment of the nose (nasal hypoplasia). Other findings may include progressive growth delays, short stature, and/or unusual head and facial (craniofacial) features. Affected infants may exhibit premature maturation of bones of the hands and feet, malformation and shortening of the forearm bones (radius and ulna) near the wrist, and/or abnormally short fingers and toes (brachydactyly). Characteristic facial features may include a flattened, underdeveloped (hypoplastic) “pug” nose, an underdeveloped upper jaw bone (maxilliary hypoplasia), widely spaced eyes (ocular hypertelorism), and/or an extra fold of skin on either side of the nose that may cover the eyes’ inner corners (epicanthal folds). It may be inherited as an autosomal dominant trait in some cases, although no gene has yet been identified with this disorder. (For more information on this disorder, choose “acrodysostosis” as your search term in the Rare Disease Database.)

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Diagnosis

A diagnosis of maxillofacial dysostosis is made based upon identification of characteristic symptoms, a detailed patient history, a thorough clinical evaluation and a variety of specialized tests to rule out other disorders.

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Standard Therapies

Treatment

The treatment of maxillofacial dysostosis is directed toward the specific symptoms that are apparent in each individual. Facial features may improve with age, often resulting in a near normal appearance by adulthood. When facial abnormalities are severe a variety of medical techniques including plastic surgery or orthodontic repair may be necessary.

Genetic counseling may be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.

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Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

Contact for additional information about maxillofacial dysostosis:

James Reynolds, MD, FAAP, FACMG

Medical Geneticist

Shodair Children’s Hospital

2755 Colonial Drive

Helena, MT 59601

Phone: 800-447-6614

Email: JReynolds@shodair.org

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References

TEXTBOOKS

Gorlin RJ, Cohen MM Jr, Hennekam RCM. Eds. Syndromes of the Head and Neck. 4th ed. New York, NY: Oxford University Press; 2001:809.

Buyse ML, ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: The Center for Birth Defects Information Services Inc; 1990:1109.

JOURNAL ARTICLES

Ensink RJH, Brunner HG, Cremers CWRJ. A new type of maxillofacial dysostosis, inherited as an x-linked recessive trait. Gen Couns. 1997;8:285-290.

Escobar V, Eastman J, Weaver D, Melnick M. Maxillofacial dysostosis. J Med Genet. 1977;14:355-358.

Melnick M, Eastman JR. Autosomal dominant maxillofacial dysostosis. Birth Defects Orig Art Ser. 1977;XIII(3B):39-44.

INTERNET.

Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Maxillofacial Dysostosis. Entry No: 155000. Last Edited March 18, 2004. Available at: https://www.ncbi.nlm.nih.gov/omim/. Accessed October 4, 2012.

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