L1 Syndrome

L1 Syndrome is an X-linked congenital neurodevelopmental disorder spanning X-linked hydrocephalus with stenosis of the aqueduct of Sylvius, MASA syndrome, complicated spastic paraplegia type 1 and X-linked corpus-callosum dysgenesis. Core features include variable hydrocephalus, developmental delay or intellectual disability, progressive lower-limb spasticity and adducted thumbs; seizures and Hirschsprung disease occur in a minority.

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Genetics

Caused by hemizygous pathogenic variants in L1CAM at Xq28 and inherited in an X-linked pattern. Truncating variants, deletions and functionally severe missense variants generally result in loss of function. Heterozygous females are usually asymptomatic or mildly affected but can rarely show clinically significant disease.

Molecular Mechanism

L1CAM encodes a neuronal immunoglobulin-superfamily cell-adhesion molecule required for axon growth and fasciculation, neuronal migration, corticospinal-tract development and neuron-glia interactions. Reduced surface expression or impaired molecular interactions disrupt neural wiring and brain development, particularly the corpus callosum and corticospinal tracts; the mechanism underlying hydrocephalus remains incompletely resolved.

Therapy

No disease-modifying therapy is established. Management is multidisciplinary and includes neurosurgical treatment of hydrocephalus when indicated, surveillance for raised intracranial pressure and seizures, physiotherapy and treatment of spasticity, developmental and communication support, and orthopedic management of adducted thumbs and contractures.

CCP Activity

CCP characterizes a genetically defined L1CAM disease model and develops preclinical endpoints for future intervention studies.

Mouse Models Mouse Models & Gene Cards

Mouse Models	Gene Cards
TBD	TBD