There are no epidemiological studies reported for SLS, however,
it has been demonstrated that in regions where there is a significant consanguinity within
the population, SLS is much more common (e.g., in the Haliwas of Halifax and Warren
Counties in North Carolina). Internationally, the same pattern is reproduced in
populations where consanguineous marriages are noted (e.g., Vasterbotten and Norrbotten
County in Sweden). In these two regions, it has been discovered that a mutation was
introduced around the 13th century. The prevalence of patients with SLS in northern
Sweden is
8.3 cases per 100,000 births, whereas the prevalence of heterozygotes is 2% and the
gene frequency is 0.01%. The overall incidence in Sweden is estimated to be around 0.6
cases per 100,000 births. A lower incidence (<1 case per 100,000 births) has been
observed worldwide. Sjögren Larsson Syndrome is estimated at 1:1000 patients with mental
retardation and in 1:2500 pediatric dermatologic patients. It is not a fatal medical
condition because most patients do not show a progressive neurodegenerative course. There
is no apparent racial predilection as well as no sexual predilection. Onset is in the
newborn period, when symptoms usually begin and the first signs of the disease (first
ichthyosis, subsequent neurologic symptoms) appear. The latter form of the disease
develops in patients aged 4-30 months.