Sjögren - Larsson Syndrome (SLS)
What is Sjögren - Larsson Syndrome?
Sjögren-Larsson Syndrome (SLS) is an inherited disorder characterized by skin abnormalities (ichthyosis) and neurologic abnormalities that appear in infancy. Ichthyosis appears as a dry, scaly skin condition, often with redness and itchiness. Neurologic abnormalities usually appear by 1-2 years of age and include tight muscles (spasticity) that impair walking, developmental delay and intellectual disability. Seizures may develop in infancy or later in childhood. Light sensitivity (photophobia) is common and changes in the back of the eye (retina) are often seen.
The key symptoms of SLS include:
- Dry, scaly skin (ichthyosis) that is usually present at birth and is often itchy
- Increased muscle tone in the arms and/or legs (spasticity)
- Intellectual disability
- Eye abnormalities and light sensitivity
- Speech difficulties
How many people have Sjögren - Larsson Syndrome?
SLS is estimated to occur in 1 per 250,000 births worldwide and higher in certain geographic locations such as Sweden and the Mideast.
What causes Sjögren - Larsson Syndrome?
SLS is caused by mutations (or changes) in the ALDH3A2 gene that makes the enzyme fatty aldehyde dehydrogenase (FALDH). FALDH is involved in the transformation of fatty aldehydes and fatty alcohols to fatty acids in our body. The gene mutations result in an inactive FALDH enzyme and accumulation of fatty aldehydes and alcohols. This is believed in turn to cause disruption in the skin-water barrier, leading to increased water loss causing dry, scaly skin, and to neurological abnormalities of spasticity, developmental delay and intellectual disability. Neurologic symptoms are associated with accumulation of lipids in the brain that can be seen on specialized MRI brain scans.
SLS is an inherited autosomal recessive disorder. Affected individuals inherit two copies of the mutated or changed ALDH3A2 gene, one from each parent. Therefore the parents are "carriers" of SLS, meaning that they have one normal functioning copy and one non functioning copy of the gene. With each pregnancy, carriers of SLS have a 1 in 4 or 25% chance of having a child with SLS.
How is Sjögren - Larsson Syndrome diagnosed?
SLS is diagnosed by measuring deficient FALDH enzyme activity in cultured skin cells or by genetic testing of the ALDH3A2 gene.
What is the treatment for Sjögren - Larsson Syndrome?
There is no curative treatment for SLS. The treatment of ichthyosis may include the use of retinoids, moisturizing lotions and keratolytic agents (peeling agent that softens and sheds the outer layer of skin). Spasticity can be treated with Botox injections and surgery. Seizures usually respond to anti-convulsant medications. All other treatments are symptomatic.