Lujan Syndrome

Symptoms, Doctors, Treatments, Advances & More

Lujan syndrome is a condition that is characterized by a tall, thin body; distinctive facial features; intellectual disabilities; and weak muscle tone (hypotonia). The condition typically affects men and boys.

Genetic changes that cause disease are called pathogenic variants. Pathogenic variants in the MED12 gene can cause Lujan syndrome. The MED12 gene provides instructions for making a protein that helps regulate gene activity and is involved in many aspects of early development. Most of the pathogenic variants in the MED12 gene that are associated with Lujan syndrome change a single protein building block (amino acid) in the MED12 protein. This genetic change likely alters the structure and function of the MED12 protein. However, it is unclear exactly how these changes lead to the intellectual disabilities and specific physical features seen in people with Lujan syndrome.

Lujan syndrome appears to be very rare, but its exact prevalence is unknown.

Lujan syndrome is inherited in an X-linked pattern. A condition is considered X-linked if the altered gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In males (who have only one X chromosome), a variant in the only copy of the gene in each cell is typically sufficient to cause the condition. Because they have two X chromosomes, females with a pathogenic variant in one copy of the MED12 gene in each cell are typically not affected.  A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

Published Date: July 09, 2026
Published By: National Institutes of Health