SLOS can present itself differently in different cases, depending on the severity of the mutation and other factors. Originally, SLOS patients were classified into two categories (classic and severe) based on physical and mental characteristics, alongside other clinical features. Since the discovery of the specific biochemical defect responsible for SLOS, patients are given a severity score based on their levels of cerebral, ocular, oral, and genital defects. It is then used to classify patients as having mild, classical, or severe SLOS. Physical characteristics The most common facial features of SLOS include microcephaly, bitemporal narrowing (reduced distance between temples), ptosis, a short and upturned nose, micrognathia, epicanthal folds, and capillary hemangioma of the nose. Other physical characteristics include: * low-set and posteriorly rotated ears * high-arched, narrow, hard palate * cleft lip/palate * agenesis or hypoplasia of the corpus callosum * cerebellar hypoplasia * increased ventricular size * decreased frontal lobe size * polydactyly of hands or feet * short, proximally placed thumb * other finger malformations * syndactyly of second and third toes * ambiguous or female-like male genitalia * congenital heart defects * renal, pulmonary, liver and eye abnormalities Syndactyly of the second and third toes Behavioural characteristics Certain behaviours and attributes are commonly seen among patients suffering from SLOS. They may have low normal intelligence, and react negatively or with hypersensitivity to different sensory stimuli. This is particularly true for certain auditory and visual stimuli. Many patients show aggressiveness and self-injurious behaviours, and sleep disturbances are common. Specific behaviours resembling those of people with autism are often present as well as hyperactivity, which provides genetic and biological insights into autism spectrum disorders. The autistic behaviours most characteristic of SLOS patients are opisthokinesis (an upper body movement), stretching of the upper body, and hand flicking. Autism is typically diagnosed separately from SLOS using the DSM-V, and approximately 50–75% of SLOS patients meet the criteria for autism. Other behaviours associated with SLOS can be linked directly to physical abnormalities. For example, infants often show feeding problems or feeding intolerance, and patients may require increased caloric intake due to accelerated metabolism. Recurrent infections, including ear infections and pneumonia, are also common. Biochemical phenotype Given that SLOS is caused by a mutation in an enzyme involved in cholesterol synthesis, the resulting biochemical characteristics may be predictable. Most patients have lowered plasma cholesterol levels (hypocholesterolemia). However, approximately 10% may show normal cholesterol levels, and decreased concentrations of cholesterol are not solely indicative of SLOS. Increased levels of cholesterol precursors are also common in SLOS. In particular, elevated levels of 7-dehydrocholesterol are fairly specific to SLOS.
Smith–Lemli–Opitz syndrome
DiGeorge syndrome
Li–Fraumeni syndrome
Smith–Magenis syndrome
Wilson–Turner syndrome
Simpson–Golabi–Behmel syndrome
Landau–Kleffner syndrome
Kapur–Toriello syndrome