High Frequency of Copy Number Variations and Sequence Variants at CYP21A2 Locus: Implication for the Genetic Diagnosis of 21-Hydroxylase Deficiency

BACKGROUND: The systematic study of the human genome indicates that the inter-individual variability is greater than expected and it is not only related to sequence polymorphisms but also to gene copy number variants (CNVs). Congenital Adrenal Hyperplasia due to 21-hydroxylase deficiency (21OHD) is the most common autosomal recessive disorder with a carrier frequency of 1:25 to 1:10. The gene that encodes 21-hydroxylase enzyme, CYP21A2, is considered to be one of the most polymorphic human genes. Copy number variations, such as deletions, which are severe mutations common in 21OHD patients, or gene duplications, which have been reported as rare events, have also been described. The correct characterization of 21OHD alleles is important for disease carrier detection and genetic counselling METHODOLOGY AND FINDINGS: CYP21A2 genotyping by sequencing has been performed in a random sample of the Spanish population, where 144 individuals recruited from university students and employees of the hospital were studied. The frequency of CYP21A2 mutated alleles in our sample was 15.3% (77.3% were mild mutations, 9% were severe mutations and 13.6% were novel variants). Gene dosage assessment was also performed when CYP21A2 gene duplication was suspected. This analysis showed that 7% of individuals bore a chromosome with a duplicated CYP21A2 gene, where one of the copies was mutated. CONCLUSIONS: As far as we know, the present study has shown the highest frequency of 21OHD carriers reported by a genotyping analysis. In addition, a high frequency of alleles with CYP21A2 duplications, which could be misinterpreted as 21OHD alleles, was found. Moreover, a high frequency of novel genetic variations with an unknown effect on 21-hydroxylase activity was also found. The high frequency of gene duplications, as well as novel variations, should be considered since they have an important involvement in carrier testing and genetic counseling

Tracking clinical genetic services for newborns identified through newborn dried bloodspot screening in the United States—lessons learned

To determine how US newborn dried bloodspot screening (NDBS) programs obtain patient-level data on clinical genetic counseling services offered to families of newborns identified through newborn NDBS and the extent to which newborns and their families receive these services. These data should serve to inform programs and lead to improved NDBS follow-up services. Collaborations were established with three state NDBS programs that reported systematically tracking genetic counseling services to newborns and their families identified through NDBS. A study protocol and data abstraction form were developed and IRB approvals obtained. Data from three state NDBS programs on a total of 151 patients indicated that genetic services are documented systematically only by metabolic clinics, most often by genetic counselors. Data from 69 endocrinology patients indicated infrequent referrals for genetic services; as expected higher for congenital adrenal hyperplasia than congenital hypothyroidism. Endocrinology patients were often counseled by physicians. While systematic tracking of genetic counseling services may be desirable for quality assurance of NDBS follow-up services, current systems do not appear conducive to this practice. Clinical records are not typically shared with NDBS programs and tracking of follow-up clinical genetic services has not been generally defined as a NDBS program responsibility. Rather, tracking of clinical services, while recognized as useful data, has been viewed by NDBS programs as a research project. The associated IRB requirements for patient-related research may pose an additional challenge. National guidance for NDBS programs that define quality genetic service indicators and monitoring responsibilities are needed. US experiences in this regard may provide information that can assist developing programs in avoiding tracking issues

International differences in the evaluation of conditions for newborn bloodspot screening: a review of scientific literature and policy documents

Despite international adoption of newborn bloodspot screening (DBS), no two countries' screening programs are the same. This article aims to understand what factors influence DBS decision-making criteria and how conditions are assessed against them. In doing so, it offers unique insights into the international landscape of DBS. A systematic review on DBS criteria in scientific literature was first undertaken. Through this, five topics were identified for consideration when analyzing DBS decision-making. Using these five topics as a template, a side-by-side comparison was conducted on DBS in policy documents of eight countries. Programs are using different approaches to explore the same policy issues, including: the beneficiary of DBS, definition of criteria, the way conditions are assessed, level of evidence required, and recommendations after assessment. These differences have the potential to result in increased disparity across DBS internationally. Ultimately, governments need to decide on their role and develop an approach to DBS decision-making in line with this role. The analyses presented in this article highlight that despite programs' commonalities, no one 'DBS decision-making solution' exists. Understanding the different approaches to decision-making within the literature and policy settings, provides an objective starting point for structured decision-making approaches for DBS programs