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L1 Syndrome

What is L1 syndrome?

L1 syndrome is a rare X-linked disorder that primarily affects the nervous system and is characterized by hydrocephalus, spasticity of the lower limbs, adducted thumbs, difficulty with speaking, seizures, and underdeveloped or absent connective tissue between the left and right parts of the brain. The condition almost exclusively occurs in males.

What causes L1 syndrome?

L1 syndrome is caused by mutations in the L1CAM gene that is located on the X chromosome. These mutations are inherited.

What are the symptoms of L1 syndrome?

The two acronyms, HSAS and MASA, are used to describe the characteristic symptoms of the variable types of L1 syndrome. Though HSAS and MASA syndrome were once thought to be distinct conditions, they are now known to be caused by mutations in the same gene and are grouped together. HSAS stands for: (H): Hydrocephalus (prenatal and severe) (S): Spasticity (A): Adducted thumbs (S): Severe intellectual disability MASA stands for: (M): Mental retardation (A): Aphasia (S): Spasticity (A): Adducted thumbs These symptoms can be either mild or severe.

How is L1 syndrome diagnosed?

L1 syndrome is diagnosed after a thorough clinical evaluation, a detailed patient and family history, and an observation of the characteristic signs and symptoms of the disease, using neuropathology and neuroimaging to reveal hydrocephalus. To confirm a diagnosis, an MRI or autopsy can reveal bilateral absence of the pyramids, which is a characteristic laboratory finding of L1 syndrome. Molecular genetic testing can also be used.

What are the available treatments for L1 syndrome?

Unfortunately, there is no cure for L1 syndrome as of yet, so treatment is symptomatic and supportive. These treatment options can include any of the following:
  • Surgery for hydrocephalus, including shunting of the cerebrospinal fluid to reduce the subsequent pressure on the brain
  • Tendon transfer or splints to help thumb function
  • Special education and/or behavioral therapy for intellectual disability and/or mental retardation

Where can I find more information on L1 syndrome?

L1 Syndrome Articles