Mabel Yau

Noninvasive Prenatal Diagnosis of Congenital Adrenal Hyperplasia Using Cell-Free Fetal DNA in Maternal Plasma

CONTEXT Congenital adrenal hyperplasia (CAH) is an autosomal recessive condition that arises from mutations in CYP21A2 gene, which encodes for the steroidogenic enzyme 21-hydroxylase. To prevent genital ambiguity in affected female fetuses, prenatal treatment with dexamethasone must begin on or before gestational week 9. Currently used chorionic villus sampling and amniocentesis provide genetic results at approximately 14 weeks of gestation at the earliest. This means that mothers who want to undergo prenatal dexamethasone treatment will be unnecessarily treating seven of eight fetuses (males and three of four unaffected females), emphasizing the desirability of earlier genetic diagnosis in utero. OBJECTIVE The objective of the study was to develop a noninvasive method for early prenatal diagnosis of fetuses at risk for CAH. PATIENTS Fourteen families, each with a proband affected by phenotypically classical CAH, were recruited. DESIGN Cell-free fetal DNA was obtained from 3.6 mL of maternal plasma. Using hybridization probes designed to capture a 6-Mb region flanking CYP21A2, targeted massively parallel sequencing (MPS) was performed to analyze genomic DNA samples from parents and proband to determine parental haplotypes. Plasma DNA from pregnant mothers also underwent targeted MPS to deduce fetal inheritance of parental haplotypes. RESULTS In all 14 families, the fetal CAH status was correctly deduced by targeted MPS of DNA in maternal plasma, as early as 5 weeks 6 days of gestation. CONCLUSIONS MPS on 3.6 mL plasma from pregnant mothers could potentially provide the diagnosis of CAH, noninvasively, before the ninth week of gestation. Only affected female fetuses will thus be treated. Our strategy represents a generic approach for noninvasive prenatal testing for an array of autosomal recessive disorders.

Long term outcomes in 46, XX adult patients with congenital adrenal hyperplasia reared as males

Patients with Congenital Adrenal Hyperplasia (CAH) owing to 21-hydroxylase deficiency and whose karyotype is 46, XX are usually assigned to the female gender. Reported herein are the long term outcomes in three patients with CAH whose karyotype is 46, XX and who were reared as males. A retrospective review of three CAH patients with a 46, XX karyotype who were reared as males was conducted. Gender assignment, clinical and biochemical data, pre and post-genitoplasty genital examinations were reviewed. Gender identity was tested by an extensive questionnaire. Gender role, sexual preference, marital status and sexual satisfaction were evaluated by interview. The three patients were genotyped for the CYP21A2 gene confirming the diagnosis of CAH. Owing to genital virilization, cultural preferences for male gender and the lack of newborn screening programs the three patients reported herein were assigned to the male gender at birth before the diagnosis of CAH was established. In adulthood the patients remained significantly virilized. Thorough psychosexual assessments in adulthood revealed well established male gender identities compatible with their male gender assignments at birth. In all three patients, gender role and behavior were consistent with male gender identity including sexual intercourse with female partners. The three patients reported herein revealed that male gender assignment to CAH patients with a 46, XX karyotype may have a successful outcome providing there is strong parental support and expert endocrine care. No standard guidelines have been published for the gender assignment of CAH patients with a 46, XX karyotype and genital ambiguity. More studies concerning gender assignment in CAH patients with a 46, XX karyotype reared as males are needed.

A rare CYP21A2 mutation in a congenital adrenal hyperplasia kindred displaying genotype-phenotype nonconcordance.

Congenital adrenal hyperplasia (CAH) owing to 21‐hydroxylase deficiency is caused by the autosomal recessive in‐heritance of mutations in the gene CYP21A2. CYP21A2 mutations lead to variable impairment of the 21‐hydroxylase enzyme, which, in turn, is associated with three clinical phenotypes, namely, salt wasting, simple virilizing, and nonclassical CAH. However, it is known that a given mutation can associate with different clinical phenotypes, resulting in a high rate of genotype–phenotype nonconcordance. We aimed to study the genotype–phenotype nonconcordance in a family with three siblings affected with nonclassical CAH. All had hormonal evidence of nonclassical CAH, but this phenotype could not be explained by the genotype obtained from commercial CYP21A2 genetic testing, which revealed heterozygosity for the maternal 30 kb deletion mutation. We performed Sanger sequencing of the entire CYP21A2 gene in this family to search for a rare mutation that was not covered by commercial testing and found in the three siblings a second, rare c.1097G>A (p.R366H) mutation in exon 8. Computational modeling confirmed that this was a mild mutation consistent with nonclassical CAH. We recommend that sequencing of entire genes for rare mutations should be carried out when genotype–phenotype nonconcordance is observed in patients with autosomal recessive monogenic disorders, including CAH.

Congenital Adrenal Hyperplasia: Unresolved Issues

Congenital adrenal hyperplasia (CAH) describes a family of disorders that comes from enzymatic deficiencies in cortisol production, with 21-hydroxylase deficiency causing ∼90% of cases. Distinction is made between the severe classical form and milder nonclassical form of CAH. Molecular genetic analysis is used to confirm the hormonal diagnosis. A high rate of genotype-phenotype disconcordance has been found in 21-hydroxylase deficiency. The goal of treatment is to replace with synthetic glucocorticoids and mineralocorticoids and suppress adrenal androgen production. The treatment of patients affected with nonclassical CAH, particularly males, remains controversial. Variable synthetic glucocorticoids are used and new modes of glucocorticoid delivery are under investigation. To improve height, growth hormone and other adjuvant therapies are employed. Long-term outcomes of genital surgery using modern techniques in females affected with classical CAH continue to be investigated. Prenatal treatment with dexamethasone is available to avoid ambiguous genitalia in these females. Although studies have shown its safety to mother and fetus, prenatal treatment is still regarded as experimental. Currently, prenatal diagnosis of CAH can only be obtained through invasive methods. Recently, the detection of cell-free fetal DNA in maternal plasma has made it possible to make this diagnosis earlier and noninvasively.

Prenatal Diagnosis of Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency is a monogenic disorder of adrenal steroidogenesis. To prevent genital ambiguity, in girls, prenatal dexamethasone treatment is administered early in the first trimester. Prenatal genetic diagnosis of CAH and fetal sex determination identify affected female fetuses at risk for genital virilization. Advancements in prenatal diagnosis are owing to improved understanding of the genetic basis of CAH and improved technology. Cloning of the CYP21A2 gene ushered in molecular genetic analysis as the current standard of care. Noninvasive prenatal diagnosis allows for targeted treatment and avoids unnecessary treatment of males and unaffected females.

Noninvasive Prenatal Diagnosis of Congenital Adrenal Hyperplasia

A major hallmark of classical congenital adrenal hyperplasia (CAH) is genital ambiguity noted at birth in affected females, which leads to psychological and psychosexual issues in adult life. Attempts to correct genital ambiguity through surgical intervention have been partially successful. Fetal hyperandrogenemia and genital ambiguity have been shown to be preventable by prenatal administration of low-dose dexamethasone initiated before the 9th week of gestation. In 7 of 8 at-risk pregnancies, the unaffected fetus is unnecessarily exposed to dexamethasone for weeks until the diagnosis of classical CAH is ruled out by invasive procedures. This therapeutic dilemma calls for early prenatal diagnosis so that dexamethasone treatment can be directed to affected female fetuses only. We describe the utilization of cell-free fetal DNA in mothers carrying at-risk fetuses as early as 6 gestational weeks by targeted massively parallel sequencing of the genomic region including and flanking the CYP21A2 gene. Our highly personalized and innovative approach should permit the diagnosis of CAH before genital development begins, therefore restricting the purposeful administration of dexamethasone to mothers carrying affected females.

Health-Related Quality of Life in Children with Congenital Adrenal Hyperplasia.

Background/Aims: Factors in congenital adrenal hyperplasia (CAH) that may affect quality of life (QOL) include the need for lifelong medication, the risk of adrenal crisis, and hyperandrogenic symptoms. The objectives were to evaluate health-related QOL (HRQOL) in children with CAH, and whether CAH poses an additional burden compared to other endocrine disorders. Methods: The validated PedsQL 4.0 generic core scales were administered to subjects (8-18 years) with CAH and hypothyroidism and their parents. The minimal clinically important difference (MCID) was determined for each scale score, allowing a comparison with the healthy population. A score of >1 standard deviation below the population mean was considered at risk for impaired HRQOL. Results: In CAH, the mean total HRQOL scores were >1 MCID below the population mean, and a higher percentage than expected had scores considered at risk. Conclusion: Compared to subjects with hypothyroidism, subjects with CAH self-reported lower school domain scores. CAH subjects more frequently reported peers not wanting to be friends.

Apparent mineralocorticoid excess and the long term treatment of genetic hypertension.

Apparent mineralocorticoid excess (AME) is a genetic disorder causing severe hypertension, hypokalemia, and hyporeninemic hypoaldosteronism owing to deficient 11 beta-hydroxysteroid dehydrogenase type-2 (11βHSD2) enzyme activity. The 11βHSD2 enzyme confers mineralocorticoid receptor specificity for aldosterone by converting cortisol to its inactive metabolite, cortisone and inactivating the cortisol-mineralocorticoid receptor complex. The 20year follow-up of a consanguineous Iranian family with three sibs affected with AME shows the successes and pitfalls of medical therapy with spironolactone. The three sibs, (female, male, female) were diagnosed at the ages of 14, 11, and 4 years, respectively. At diagnosis, hypertensive retinopathy and left ventricular hypertrophy were present in the eldest female and retinopathy was noted in the male sib. Spironolactone treatment resulted in decreased blood pressure and rise in serum potassium levels. The older female, age 36, developed reduced left ventricular function with mitral and tricuspid regurgitation and renal failure after her second pregnancy. She was treated with renal transplantation resulting in cure of AME with decreased blood pressure and weaning from antihypertensives. Her younger sibs, age 34 and 26, do not have end organ damage. Early and vigilant treatment improves morbidity in patients with AME. Mineralocorticoid receptor antagonists normalize blood pressure, correct hypokalemia and reduce hypertensive end-organ damage in patients with AME. Low dose dexamethasone can be considered, though the response may be variable. Future directions of therapy include selective mineralocorticoid antagonists.

Clinical, genetic, and structural basis of apparent mineralocorticoid excess due to 11β-hydroxysteroid dehydrogenase type 2 deficiency

Significance Apparent mineralocorticoid excess, a rare autosomal recessive disorder characterized by low renin hypertension, may display a severe or mild phenotype in patients. The variability in clinical presentation stems from different extents of impairment of the 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) enzyme arising from distinct mutations in the encoding gene. The computational model of the HSD11B2 protein that we constructed here will be useful in predicting disease severity for newly reported missense mutations in this gene. Mutations in 11β-hydroxysteroid dehydrogenase type 2 gene (HSD11B2) cause an extraordinarily rare autosomal recessive disorder, apparent mineralocorticoid excess (AME). AME is a form of low renin hypertension that is potentially fatal if untreated. Mutations in the HSD11B2 gene result either in severe AME or a milder phenotype (type 2 AME). To date, ∼40 causative mutations have been identified. As part of the International Consortium for Rare Steroid Disorders, we have diagnosed and followed the largest single worldwide cohort of 36 AME patients. Here, we present the genotype and clinical phenotype of these patients, prominently from consanguineous marriages in the Middle East, who display profound hypertension and hypokalemic alkalosis. To correlate mutations with phenotypic severity, we constructed a computational model of the HSD11B2 protein. Having used a similar strategy for the in silico evaluation of 150 mutations of CYP21A2, the disease-causing gene in congenital adrenal hyperplasia, we now provide a full structural explanation for the clinical severity of AME resulting from each known HSD11B2 missense mutation. We find that mutations that allow the formation of an inactive dimer, alter substrate/coenzyme binding, or impair structural stability of HSD11B2 yield severe AME. In contrast, mutations that cause an indirect disruption of substrate binding or mildly alter intramolecular interactions result in type 2 AME. A simple in silico evaluation of novel missense mutations could help predict the often-diverse phenotypes of an extremely rare monogenic disorder.

A novel mutation in HSD11B2 causes apparent mineralocorticoid excess in an Omani kindred.

Apparent mineralocorticoid excess (AME) is a rare autosomal recessive genetic disorder causing severe hypertension in childhood due to a deficiency of 11β‐hydroxysteroid dehydrogenase type 2 (11βHSD2), which is encoded by HSD11B2. Without treatment, chronic hypertension leads to early development of end‐organ damage. Approximately 40 causative mutations in HSD11B2 have been identified in ∼100 AME patients worldwide. We have studied the clinical presentation, biochemical parameters, and molecular genetics in six patients from a consanguineous Omani family with AME. DNA sequence analysis of affected members of this family revealed homozygous c.799A>G mutations within exon 4 of HSD11B2, corresponding to a p.T267A mutation of 11βHSD2. The structural change and predicted consequences owing to the p.T267A mutation have been modeled in silico. We conclude that this novel mutation is responsible for AME in this family.