What is the US prevalence of Smith-Lemli-Opitz syndrome (SLOS)?

Updated: Jan 27, 2021
  • Author: Robert D Steiner, MD; Chief Editor: Luis O Rohena, MD, MS, FAAP, FACMG  more...
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United States

Prevalence of Smith-Lemli-Opitz syndrome has been estimated to be 1 in 20,000-60,000 births among Caucasians. Smith-Lemli-Opitz syndrome is also not uncommon in Hispanics. Its specific prevalence in different populations has not been precisely determined. The higher-than-expected prevalence of Smith-Lemli-Opitz syndrome suggests a heterozygote advantage.

Only one description of an African-American patient has been published, although no biochemical or molecular confirmation of Smith-Lemli-Opitz syndrome was available. [9] In a study of 150 biochemically diagnosed patients with Smith-Lemli-Opitz syndrome, only one individual was of African descent. [10] In 2000, Yu and colleagues did not detect the mutation among 121 Africans from Sierra Leone. [11] In 2001, Nowaczyk and colleagues reported an IVS8-1G>C (common Smith-Lemli-Opitz syndrome mutation) carrier frequency of 1.09% (17 per 1559 population) in Canadian whites and 0.79% (4 per 504 population) in Canadians of African descent; however, no African Canadian patients were identified. [12]

The results of Wright et al's 2003 study indicate an IVS8-1G>C carrier frequency of 0.73% (10 per 1378 population) in African Americans. [13] This predicts the prevalence of Smith-Lemli-Opitz syndrome due to IVS8-1G>C homozygosity to be 1 case per 75,061 persons in the African American population. Although the African American carrier frequency of the IVS8-1G>C allele was determined to be 0.73%, few African American patients with Smith-Lemli-Opitz syndrome have been identified.

Carrier frequency for Smith-Lemli-Opitz syndrome is approximately 1 in 30 persons of northern European descent, suggesting a disease frequency of 1 per 5000-18,000 people. The actual disease prevalence may be lower because of fetal losses and missed diagnoses or misdiagnoses at the most severe and most mild ends of the severity spectrum.

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