Reviewed March 2008
What is L1 syndrome?
L1 syndrome is an inherited disorder that primarily affects the nervous system. L1 syndrome involves a variety of features that were once thought to be distinct disorders, but are now considered to be part of the same syndrome. The most common characteristics of L1 syndrome are muscle stiffness (spasticity) of the lower limbs, mental retardation, increased fluid in the center of the brain (hydrocephalus), and thumbs bent toward the palm (adducted thumbs). People with L1 syndrome can also have difficulty speaking (aphasia), seizures, and underdeveloped or absent tissue connecting the left and right halves of the brain (agenesis of the corpus callosum). The symptoms of L1 syndrome vary widely among affected individuals, even among members of the same family. Because this disorder involves spasticity of the lower limbs, L1 syndrome is sometimes referred to as spastic paraplegia type 1 (SPG1).
How common is L1 syndrome?
L1 syndrome is estimated to occur in 1 in 25,000 to 60,000 males. Females are rarely affected by this condition.
What genes are related to L1 syndrome?
L1 syndrome is caused by mutations in the L1CAM gene. The L1CAM gene provides instructions for producing the L1 protein, which is found throughout the nervous system on the surface of nerve cells (neurons). The L1 protein plays a role in the development and organization of neurons, the formation of the protective sheath (myelin) that surrounds certain neurons, and the formation of junctions between nerve cells (synapses), where cell-to-cell communication occurs. Mutations in the L1 protein can interfere with these developmental processes. Research suggests that a disruption in the development and function of neurons causes the signs and symptoms of L1 syndrome.
Read more about the L1CAM gene.
How do people inherit L1 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 striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
Where can I find information about treatment for L1 syndrome?
These resources address the management of L1 syndrome and may include treatment providers.
You might also find information on treatment of L1 syndrome in
Educational resources and Patient support.
Where can I find additional information about L1 syndrome?
You may find the following resources about L1 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 L1 syndrome?
- CRASH syndrome
- MASA syndrome
- X-linked complicated hereditary spastic paraplegia type 1
- X-linked corpus callosum agenesis
- X-linked hydrocephalus with stenosis of the aqueduct of Sylvius (HSAS)
What if I still have specific questions about L1 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 L1 syndrome?
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
See How can I find a genetics professional in my area? in the Handbook.