Sjögren-Larsson syndrome (SLS) is a rare inherited neurocutaneous disorder resulting from mutations in the ALDH3A2 gene encoding fatty aldehyde dehydrogenase (FALDH), an enzyme responsible for catalysing the oxidation of fatty aldehyde to fatty acid. This mutation leads to the accumulation of fatty alcohols and aldehydes causing abnormalities within the skin, eyes, and brain.
Clinical features: The classic clinical triad is characterised by ichthyosis, intellectual disability, and spastic diplegia, or less commonly, spastic tetraplegia. The first symptom of SLS is typically generalised ichthyosiform hyperkeratosis, which is often present from birth or early infancy. The skin condition tends to be associated with pruritus and is prevalent in the neck, trunk, and flexures, sparing the face. Heat intolerance secondary to hypohydrosis has been reported. The neurologic symptoms present as developmental delay in the first one to two years of life, often with delayed motor milestones. Spasticity with weakness in the lower limbs, more than the upper limbs, reflects spastic diplegia and most individuals require assistance with walking. The intellectual disability varies from mild to severe. Seizures occur in about 40 % of patients, but are usually well controlled with antiepileptic medications. Language problems prevail and include dysarthria and speech delays. The distinct ophthalmologic finding is crystalline retinopathy which manifests as glistening white dots in the macula, usually in the parafoveal area. Patients often suffer from impaired visual acuity and photophobia. Kyphoscoliosis and short stature have been reported. The prevalence of SLS is around 0.4 in 100,000.
Diagnosis and treatment: Due to phenotypic variability and presentation following a typical age-dependent pattern, diagnosis can be difficult in young children. The classic triad is often not present until age 3. DNA diagnosis is now preferred, although originally fibroblast cultures were grown from skin biopsies for enzymatic testing. Brain MRI shows periventricular white matter abnormalities, which may represent dysmyelination. There is currently no treatment for SLS other than supportive care which may include topical treatments for ichthyosis, anti-epileptic medications for seizures, and surgical procedures or botulinum toxin injections to relieve spasticity. Physical therapy and speech therapy are important to optimise daily functioning.