Lujan-Fryns syndrome, also called X-linked mental retardation with marfanoid habitus syndrome, is a genetic condition that causes significant learning issues (intellectual disabilities), behavioral problems, and abnormal physical features, including a tall, thin stature with long arms and legs. These physical features are seen in another condition, known as Marfan syndrome, which is where the term ‘marfanoid habitus’ comes from. Other features of the condition can include a large head (macrocephaly), a long, thin face, large forehead, pointed nose, small space between the nose and mouth (philtrum), narrow roof of the mouth, crowded teeth, loose joints, and weak muscle tone (hypotonia). Behavioral problems include aggression, attention seeking, and even hallucinations. Some children with this condition have heart defects and abnormalities in the tissue that connects the left and right halves of the brain (corpus callosum). Because of the way it is inherited, this condition usually only affects males.
This condition is caused by a change (mutation) in the MED12 gene and is inherited in an X-linked recessive way. Males have one X chromosome (one copy of the MED12 gene) and females have two X chromosomes (two copies of the MED12 gene). Males who have a mutation in their one copy of the gene will have the condition, while females who have a mutation in only one of the two copies usually do not show signs of the condition.
The diagnosis of Lujan-Fryns syndrome is considered in a tall, thin male who has significant learning issues. Genetic testing is used to confirm the diagnosis. Therapies can help affected children reach their developmental potential. If your child has been diagnosed with this condition, talk with their doctor about all treatment options. Support groups can provide additional information.