Isolated autism is not an indication for SLO testing

Abstract

Study Smith-Lemli-Opitz (SLO) syndrome is an autosomal recessive disorder of cholesterol synthesis due to deficiency in 7-dehydrocholesterol (7-DHC) reductase. SLO is associated with specific dysmorphology, microcephaly, syndactyly, cleft palate, growth retardation, genital ambiguity and intellectual disability with autistic features. The autistic features respond to cholesterol supplementation. Increased levels of 7-DHC are a marker for SLO and routinely used for testing of autistic children. Methods A total of 5 years of requests for 7-DHC testing at S A Pathology were audited (2008-2012). Data were broadly classified according to clinical indications, including isolated autism, developmental delay, seizure, dysmorphism, neurological, anatomic, genital or metabolic anomalies. Data were sub-classified as single or multiple clinical indication/s or no clinical information supplied. Results 809 tests were performed and 16 cases of SLO were detected. No cases of SLO were diagnosed based on an isolated clinical indication of autism or where no clinical information was supplied. Discussion Experience of several years of 7-DHC testing at SA Pathology indicates that autism as an isolated clinical trait is not associated with SLO. 7-DHC measurement should not be included in the testing panel when autism spectrum disorders are the only clinical indication.