The Sjögren-Larsson syndrome (SLS) is a genetically determined syndrome with autosomal recessive inheritance originally and comprehensively described from Sweden. It is characterized by the three cardinal signs congenital ichthyosis, spastic di- or tetraplegia and mental retardation.The present investigation covers all 35 SLS patients alive in Sweden in 1978 and the genetic study all 58 SLS patients born in Sweden in 1886-1977. Forty-five of these were bom in a restricted area in the northeast of Sweden and five more had ancestors from this area. This concentration is probably the result of a founder effect — transmission of the SLS gene mutation from early immigrants to this area — followed by little migration to and from this area. Ancestors of SLS patients have been traced back to an early immigrant to this area in the 14th century.The mean yearly incidences of SLS per 100.000 newborn during the years 1901-1977 were 0.6 in the whole of Sweden, 10.2 in the county of Västerbotten and 2.7 in the county of Norrbotten. The corresponding prevalence figures for SLS on 31 December 1978 were 0.4, 8.3 and 2.6 per 100.000 in these areas, respectively.The ichthyosis in the SLS was found to be congenital in the true sense of the word, as it was always seen at birth. The characteristic skin findings indicate that the use of replicas in ichthyotic patients may be a good complement to the clinical and histopathological examinations.All SLS patients had mental retardation and spastic di- or tetraplegia. The first observation of these symptoms was made between the age of 4 and 30 months.Small white glistening dots located in the ocular fundus were noted in all 30 SLS patients examined in this respect and seem to be pathognomonic for SLS.The fatty acid patterns of plasma phospholipids, cholesteryl esters, triglycerides and free fatty acids in SLS patients were examined. The results suggest that SLS is possibly a disorder of fatty acid metabolism leading to an altered composition of polyunsaturated fatty acids due to a disturbance in the A6-desaturation of essential fatty acids. / <p>Some photos have been censored.</p><p>En del foton har blivit censurerade.</p> / digitalisering@umu