Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder. It is due to a deficiency of 7-dehydrocholesterol reductase (DHCR7) that catalyses the reduction of 7-dehydrocholesterol (7-DHC) to cholesterol. The aim of this review is to gather all information, concerning diagnostic characteristics of this syndrome, with an emphasis on intraoral symptom presentation. We conducted a review of the literature, including articles between 1964 and 2017. Data was collected regarding the clinical diagnosis, pathophysiology and treatment of SLOS patients. Moreover, two clinical cases are described, illustrating the oral and facial anomalies of SLOS patients, at the regional university hospital of Lille, France. Low cholesterol levels provoke a broad spectrum of clinical presentations, from mild to lethal forms. They can cause mental retardation, growth deficiency and congenital malformations. The SLOS features are often present at birth. Moreover, all the patients have facial anomalies. The dento-maxillofacial symptoms consist of crowded teeth, widely spaced incisors, oligodontia, polydontia, premature tooth eruption, enamel hypoplasia, a bifid uvula, broad alveolar ridges, bifid tongue, and Pierre-Robin syndrome symptoms (glossoptosis, retrognathia and cleft palate). These symptoms are warning signs and should increase the awareness of clinicians. All healthcare professionals can contribute to the SLOS patient diagnostics. The dento-maxillofacial anomalies, illustrated by two case reports, could help to detect undiagnosed patients. An early detection might improve the outcome of these patients, as cholesterol supplementation can improve symptoms. This study can benefit orthodontists by enabling them to recognize the clinical signs of SLOS in order to refer these young patients to a specialist if the diagnosis has not been established.