PRENATAL DIAGNOSIS Prenat Diagn 2010; 30: 893–898. Published online 16 August 2010 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/pd.2588 Prevalence of steroid sulfatase deficiency in California according to race and ethnicity Wendy Y. Craig 1 *, Marie Roberson 2 , Glenn E. Palomaki 3 , Cedric H. L. Shackleton 4 , Josep Marcos 5 and James E. Haddow 3 1 Foundation for Blood Research, Scarborough, ME, USA 2 California Department of Public Health, Genetic Disease Screening Program, Richmond, CA, USA 3 Department of Pathology and Laboratory Medicine, Women & Infants Hospital, Warren Alpert Medical School at Brown University, Providence, RI, USA 4 Children’s Hospital Oakland Research Institute, Oakland, CA, USA 5 Institut Municipal d’Investigaci´ o M` edica, Barcelona, Spain Objective Estimate steroid sulfatase deficiency (STSD) prevalence among California’s racial/ethnic groups using data from a previous study focused on prenatal detection of Smith-Lemli-Opitz syndrome (SLOS). SLOS and STSD both have low maternal serum unconjugated estriol (uE3) levels. Methods Prevalence was estimated using three steps: listing clinically identified cases; modeling STSD frequency at three uE3 intervals using diagnostic urine steroid measurements; applying this model to determine frequency in pregnancies not providing urine. Results Overall, 2151 of 777 088 pregnancies (0.28%) were screen positive; 1379 of these were explained and excluded. Fifty-four cases were diagnosed clinically among 707 remaining pregnancies with a male fetus. Urine steroid testing identified 74 additional STSD cases: 66 (89.2%) at uE3 values <0.15 MoM, 8 (10.8%) at 0.15–0.20 MoM, and 0 (0%) at >0.20 MoM. Modeling estimated 107.5 STSD cases among 370 pregnancies without urine samples. In males, STSD prevalence was highest among non-Hispanic Whites (1 : 1230) compared to Hispanics (1 : 1620) and Asians (1 : 1790), but differences were not significant. No STSD pregnancies were found among 65 screen positive Black women. Conclusion The overall prevalence estimate of 1 : 1500 males is consistent with published estimates and is reasonable for counseling, except among Black pregnancies where no reliable estimate could be made. Copyright  2010 John Wiley & Sons, Ltd. KEY WORDS: steroid sulfatase deficiency; prevalence; race/ethnicity; California INTRODUCTION Steroid sulfatase deficiency (STSD), or x-linked ich- thyosis, is an inherited skin disorder characterized by dark adherent scales. Affected male infants typically develop this phenotype within the first year of life; some also present with mild corneal opacities and/or cryp- torchidism (Ballabio and Shapiro, 2001) and later may develop attention deficit hyperactivity disorder (Kent et al., 2008). Based on two small studies (Kent et al., 2008; Langlois, 2009), about 10% of STSD cases may also be associated with a variable contiguous gene dele- tion syndrome (CGDS) (Marcos et al., 2009), which may include Kallman syndrome, mental retardation, chondrodysplasia punctata, short stature, and/or autism spectrum disorders (Ballabio et al., 1989). The rate of CGDS could be considerably higher than this estimate among sporadic STSD cases and lower among famil- ial cases. Pregnancies with uncomplicated STSD are associated with an absence of anatomic abnormalities (other than by chance) and an undetectable or low level *Correspondence to: Wendy Y. Craig, Foundation for Blood Research, PO Box 190, 8 Science Park Road Scarborough, ME 04070, USA. E-mail: wcraig@fbr.org of maternal serum unconjugated estriol (uE3) (Taylor and Shackleton, 1979; Glass et al., 1998; Ballabio and Shapiro, 2001). In the past, STSD was associated with pregnancy complications resulting from delayed onset and prolongation of labor, but current obstetrical prac- tice appears to deal successfully with these problems (Bradley et al., 1997). Several published estimates exist for STSD prevalence (Lykkesfeldt et al., 1984; Bartels et al., 1994; David et al., 1995; Schleifer et al., 1995; Schoen et al., 2003; Jari et al., 2004; Langlois et al., 2009) but none of these stratify rates by race/ethnicity. We recently reported that the combination of 16α-OH-dehydroepiandrosterone sulfate (16α-OH-DHEAS) and total estriol measure- ments in maternal urine is an effective diagnostic test for STSD when applied to pregnancies with male fetuses and very low or undetectable maternal serum uE3 lev- els (Marcos et al., 2009). These analyses were carried out as part of a multi-center population-based study, the primary purpose of which was to determine the feasi- bility of adding a Smith-Lemli-Opitz syndrome (SLOS) screening algorithm to routine prenatal screening for Down syndrome. SLOS is also associated with low maternal serum uE3 levels (Bradley et al., 1999). Data Copyright  2010 John Wiley & Sons, Ltd. Received: 20 April 2010 Revised: 7 June 2010 Accepted: 10 June 2010 Published online: 16 August 2010