Should 21-hydroxylase deficiency genotyping be considered in assisted reproductive technology programs?

The management of congenital adrenal hyperplasia during preconception, pregnancy, and postpartum

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders of steroidogenesis of the adrenal cortex, most commonly due to 21-hydroxylase deficiency caused by mutations in the CYP21A2 gene. Although women with CAH have decreased fecundity, they are able to conceive; thus, if pregnancy is not desired, contraception options should be offered. If fertility is desired, women with classic CAH should first optimize glucocorticoid treatment, followed by ovulation induction medications and gonadotropins if needed. Due to the possible pregnancy complications and implications on the offspring, preconception genetic testing and counseling with a high-risk obstetrics specialist is recommended. For couples trying to avoid having a child with CAH, care with a reproductive endocrinology and infertility specialist to utilize in vitro fertilization can be offered, with or without preimplantation genetic testing for monogenic disorders. Prenatal screening and diagnosis options during pregnancy include maternal serum cell free-DNA for sex of the baby, and chorionic villus sampling and amniocentesis for diagnosis of CAH. Pregnant women with classic CAH need glucocorticoids to be adjusted during the pregnancy, at the time of delivery, and postpartum, and should be monitored for adrenal crisis. Maternal and fetal risks may include chorioamnionitis, maternal hypertension, gestational diabetes, cesarean section, and small for gestational age infants. This review on CAH due to 21-hydroxylase deficiency highlights reproductive health including genetic transmission, contraception options, glucocorticoid management, fertility treatments, as well as testing, antenatal monitoring, and management during pregnancy, delivery, and postpartum.

Molecular Diagnosis of Steroid 21-Hydroxylase Deficiency: A Practical Approach

Adrenal insufficiency in paediatric patients is mostly due to congenital adrenal hyperplasia (CAH), a severe monogenic disease caused by steroid 21-hydroxylase deficiency (21-OHD, encoded by the CYP21A2 gene) in 95% of cases. CYP21A2 genotyping requires careful analyses that guaranty gene-specific PCR, accurate definition of pseudogene-gene chimeras, gene duplications and allele dropout avoidance. A small panel of well-established disease-causing alterations enables a high diagnostic yield in confirming/discarding the disorder not only in symptomatic patients but also in those asymptomatic with borderline/positive results of 17-hydroxyprogesterone. Unfortunately, the complexity of this locus makes it today reluctant to high throughput techniques of massive sequencing. The strong relationship existing between the molecular alterations and the degree of enzymatic deficiency has allowed genetic studies to demonstrate its usefulness in predicting/classifying the clinical form of the disease. Other aspects of interest regarding molecular studies include its independence of physiological variations and analytical interferences, its usefulness in the diagnosis of simple virilizing forms in males and its inherent contribution to the genetic counseling, an aspect of great importance taking into account the high carrier frequency of CAH in the general population. Genetic testing of CYP21A2 constitutes an irreplaceable tool to detect severe alleles not just in family members of classical forms but also in mild late-onset forms of the disease and couples. It is also helpful in areas such as assisted reproduction and preimplantation diagnosis. Molecular diagnosis of 21-OHD under expert knowledge definitely contributes to a better management of the disease in every step of the clinical course.

EMQN best practice guidelines for molecular genetic testing and reporting of 21-hydroxylase deficiency

Molecular genetic testing for congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is offered worldwide and is of importance for differential diagnosis, carrier detection and adequate genetic counseling, particularly for family planning. In 2008 the European Molecular Genetics Quality Network (EMQN) for the first time offered a European-wide external quality assessment scheme for CAH (due to 21-OH deficiency). The interest was great and over the last years at about 60 laboratories from Europe, USA and Australia regularly participated in that scheme. These best practice guidelines were drafted on the basis of the extensive knowledge and experience got from those annually organized CAH-schemes. In order to obtain the widest possible consultation with practicing laboratories the draft was therefore circulated twice by EMQN to all laboratories participating in the EQA-scheme for CAH genotyping and was updated by that input. The present guidelines address quality requirements for diagnostic molecular genetic laboratories, as well as criteria for CYP21A2 genotyping (including carrier-testing and prenatal diagnosis). A key aspect of that article is the use of appropriate methodologies (e.g., sequencing methods, MLPA (multiplex ligation dependent probe amplification), mutation specific assays) and respective limitations and analytical accuracy. Moreover, these guidelines focus on classification of variants, and the interpretation and standardization of the reporting of CYP21A2 genotyping results. In addition, the article provides a comprehensive list of common as well as so far unreported CYP21A2-variants.

The importance and implications of preconception genetic testing for accurate fetal risk estimation in 21-hydroxylase congenital adrenal hyperplasia (CAH)

Preconception genetic testing should be offered to all patients with 21-hydroxylase congenital adrenal hyperplasia. We report how the preconception genetic testing of a lady and her partner dramatically changed the estimated risk to their offspring and the major implications the results had on pregnancy planning. The risk of conceiving a female fetus with congenital adrenal hyperplasia brings in considerations of prenatal dexamethasone therapy and prenatal diagnosis. We also highlight the differences between genetic testing on a research and clinical basis.

Carrier detection and prenatal diagnosis of congenital adrenal hyperplasia must identify 'apparently mild' CYP21A2 alleles which associate neonatal salt-wasting disease

OBJECTIVE

Couples at risk of severe congenital adrenal hyperplasia (CAH) may be offered prenatal treatment or preimplantation diagnosis. However, proper genetic counselling requires the accurate identification of apparently 'mild alleles' in partners of CAH-carriers/patients.

METHODS

CYP21A2 gene analyses were performed in 255 patients with severe 21-hydroxylase deficiency (21-OHD), 94 with mild 21-OHD, 752 parental samples, 233 clinically unaffected partners and 253 historic DNA samples. GENSCAN and ClustalX2.0 software were used for in silico analyses, and Epidat 3.1 software for statistical calculations.

RESULTS

Twenty-seven partners were carriers of p.Val282Leu (alias p.Val281Leu, allele frequency 11.7%, 7.4-16.1). 'Val282Leu alleles' were detected in 30 patients with salt-wasting (SW) disease, 21 with other pseudogene-derived and rare coding cis severe mutations, and 9 without. These CYP21A2 genes were compared to those of 94 fully characterized patients with mild deficiency carrying p.Val282Leu in compound heterozygosity with a severe allele. A rare intronic variant, c.292+5G>A, was detected in the nine 'severe Val282Leu alleles' and that was not seen in mild p.Val282Leu alleles, in other deficient alleles or in normal chromosomes. The in silico documented effect on splicing and the clinical association (p < 0.0001) confirmed p.Val282Leu; c.292+5G>A as a severe allele.

CONCLUSION

As only severe alleles require clinical intervention, CAH-carrier detection of p.Val282Leu should be followed by the analysis of c.292+5G>A.