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Reviewed December 2012
What is Lujan syndrome?
Lujan syndrome is a condition characterized by intellectual disability, behavioral problems, and certain physical features. It occurs almost exclusively in males.
The intellectual disability associated with Lujan syndrome is usually mild to moderate. Behavioral problems can include hyperactivity, aggressiveness, extreme shyness, and excessive attention-seeking. Some affected individuals have features of autism or related developmental disorders affecting communication and social interaction. A few have been diagnosed with psychiatric problems such as delusions and hallucinations.
Characteristic physical features of Lujan syndrome include a tall, thin body and an unusually large head (macrocephaly). Affected individuals also have a long, thin face with distinctive facial features such as a prominent top of the nose (high nasal root); a short space between the nose and the upper lip (philtrum); a narrow roof of the mouth (palate); crowded teeth; and a small chin (micrognathia). Almost all people with this condition have weak muscle tone (hypotonia).
Additional signs and symptoms of Lujan syndrome can include abnormal speech, heart defects, and abnormalities of the genitourinary system. Many affected individuals have long fingers and toes with an unusually large range of joint movement (hyperextensibility). Seizures and abnormalities of the tissue that connects the left and right halves of the brain (corpus callosum) have also been reported in people with this condition.
How common is Lujan syndrome?
Lujan syndrome appears to be an uncommon condition, but its prevalence is unknown.
What genes are related to Lujan syndrome?
Lujan syndrome is caused by at least one mutation in the MED12 gene. This gene provides instructions for making a protein that helps regulate gene activity; it is involved in many aspects of early development. The MED12 gene mutation that causes Lujan syndrome changes a single protein building block (amino acid) in the MED12 protein. This genetic change alters the structure, and presumably the function, of the MED12 protein. However, it is unclear how the mutation affects development and leads to the cognitive and physical features of Lujan syndrome.
Read more about the MED12 gene.
How do people inherit Lujan syndrome?
This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
Where can I find information about diagnosis or management of Lujan syndrome?
These resources address the diagnosis or management of Lujan syndrome and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about Lujan syndrome?
You may find the following resources about Lujan syndrome helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for Lujan syndrome?
What if I still have specific questions about Lujan syndrome?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding Lujan syndrome?
amino acid ; autism ; cell ; chromosome ; corpus callosum ; disability ; gene ; genitourinary system ; hallucinations ; hyperactivity ; hypotonia ; inheritance ; inherited ; joint ; macrocephaly ; mental retardation ; micrognathia ; muscle tone ; mutation ; palate ; philtrum ; prevalence ; protein ; recessive ; sex chromosomes ; spectrum ; syndrome ; tissue ; X-linked recessive
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (5 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.