Smith–Lemli–Opitz syndrome
| Smith–Lemli–Opitz syndrome | |
|---|---|
 |
|
| 7-Dehydrocholesterol | |
| Classification and external resources | |
| Specialty | medical genetics |
| ICD-10 | Q87.1 |
| ICD-9-CM | 759.89 |
| OMIM | 270400 |
| DiseasesDB | 12223 |
| eMedicine | ped/2117 |
| Patient UK | Smith–Lemli–Opitz syndrome |
| MeSH | D019082 |
Smith–Lemli–Opitz syndrome (also SLOS, or 7-dehydrocholesterol reductase deficiency) is an inborn error of cholesterol synthesis. It is an autosomal recessive, multiple malformation syndrome caused by a mutation in the enzyme 7-Dehydrocholesterol reductase, or DHCR7. It causes a broad spectrum of effects, ranging from mild intellectual disability and behavioural problems to lethal malformations.
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 external behaviours, physical characteristics, and 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.
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:
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. Interestingly, specific autistic behaviours and hyperactivity are often present with SLOS, 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-IV, and approximately 50–75% of SLOS patients meet the criteria for autism.
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