A novel semiquantitative polymerase chain reaction/enzyme digestion-based method for detection of large scale deletions/conversions of the CYP21 gene and mutation screening in Turkish families with 21-hydroxylase deficiency

Genetic profiling of CAH Egyptian children: rapid guide to clinical interpretation of common mutations

OBJECTIVES

The prevalence of CAH in Egypt is reported to be ten times more than that of the worldwide prevalence. The study aimed at genetic screening of children diagnosed with 21-alpha hydroxylase deficiency congenital adrenal hyperplasia (21OHD-CAH). In addition, the study offers a rapid and easy guide for clinical reporting of common mutations for endocrinologists.

METHODS

A cohort of 174 unrelated Egyptian children with 21OHD-CAH were screened for 11 common CYP21A2 gene mutations using a strip hybridization assay, and then, bioinformatics analysis was done to report the pathogenicity of the common mutations for clinical classification.

RESULTS

The most common mutations were I2 splice and p.Q318X. Deletions/conversions comprised 45.9% of the cohort, whereas 7.4% of the cases were negative for all mutations. The least positively detected point mutations were p.P453S, cluster E6, p.R483P, and p.L307FS, which were detected in fewer than 5% of cases.

CONCLUSION

Strip hybridization assay is a rapid screening tool for the diagnosis of CAH. The authors hypothesized an easy and rapid scheme for clinical interpretation of the strip results to gain the highest value of the strip in diagnosis.

The distribution of intrafamilial CYP21A2 mutant alleles and investigation of clinical features in Turkish children and their siblings in Southeastern Anatolia

Background The genotype-phenotype relationship shows regional variability in 21-hydroxylase deficiency (21-OHD) caused by mutations in the CYP21A2 gene. This study focuses on the genotype-phenotype compatibility between patients and their siblings in a region where consanguineous marriage is common. Methods The most common mutations (I2G-P30L-I172N-V237E-M239K-V281L-Q318X-R356W-F306 + nt) were studied in 60 children with 21-OHD and 40 siblings (12 symptomatic and 28 asymptomatic; mean age 5.89 ± 4.63 and 8.34 ± 2.22 years, respectively). The allele number (patients; 93 siblings; 70 alleles) was counted for each case. Salt wasting (SW; n = 38), simple virilizing (SV; n = 11) and non-classical congenital adrenal hyperplasia (NCCAH; n = 11) types were compared with their genotypes classified into groups Null-AB-C-D-E based on enzyme impairment. Results Disease-causing mutations were identified in unrelated alleles: 80 out of 93 alleles (86%) in the patients: SW, 51/56 (91%); SV, 14/16 (87.4%) and NCCAH, 15/21 (71.4%). There were 43 out of 70 alleles (61.4%) in the siblings (asymptomatic, 25/50 [50%]; symptomatic, 18/20 [90%]). The most frequently detected mutations in the patients were: I2G (22%), Q318X-P30L-V281L (13% each). The distribution of the most common mutations by clinical types was: SW: I2G-Q318X (30.2%-19.6%), SV: I172NI2G (37.5%-18.7%), NCCAH: V281L-P30L (33.3%-28.5%). In patients and symptomatic siblings, the concordance percentages by genotype groups were: Null (100%-100%), A (85%-60%), B (100%-Not applicable), C (41.6%-50%). Eleven out of 28 asymptomatic siblings had disease-causing mutations (four, severe; one, moderate; six, mild). The distribution of genotypes by phenotypes were: SW: Null-A (88%), SV: B-A (50%-41.6%), NCCAH: C (100%). Conclusions This study showed that the most common alleles were IN2G-Q381X-R356W-P30L-V281L in the children with 21-OHD and asymptomatic siblings, and that the phenotype can be predicted from the genotype except for the P30L-V281L. This result suggests that the most common mutations in 21-OHD are similar to previous reports, but that the genotype-phenotype compatibility is good except for group C showing regional variability, and that genotyping of siblings discovered new patients.

The frequency and the effects of 21-hydroxylase gene defects in congenital adrenal hyperplasia patients

Congenital adrenal hyperplasia (CAH) is a group of genetic endocrine disorders, caused by enzyme deficiencies in the conversion of cholesterol to cortisol. More than 90% of the cases have 21-hydroxylase deficiency (21-OHD). The clinical phenotype of the disease is classified as classic, the severe form, and nonclassic, the mild form. In this study, it was planned to characterize the mutations that cause 21-OHD in Turkish CAH patients by direct sequencing and multiplex ligation-dependent probe amplification (MLPA) analysis and to investigate the type of CAH (classic or nonclassic type) that these mutations cause. A total of 124 CAH patients with 21-OHD and 100 healthy volunteers were recruited to the study. Most of the mutations were detected by direct sequencing. Large gene deletions/duplications/conversions were investigated with MLPA analysis. Results were evaluated statistically. At the end of our study, 66 different variations were detected including SNPs and deletions/duplications/conversions. Of these variations, 18 are novel, of which three cause amino acid substitutions. In addition, 15 SNPs which cause amino acid changes were identified among these variations. If similar results are obtained in different populations, these mutations, in particular the novel mutation 711 G>A, may be used as markers for prenatal diagnosis.

Prevalence of nonclassic congenital adrenal hyperplasia in Turkish children presenting with premature pubarche, hirsutism, or oligomenorrhoea

Background. Nonclassic congenital adrenal hyperplasia (NCAH), caused by mutations in the gene encoding 21-hydroxylase, is a common autosomal recessive disorder. In the present work, our aim was to determine the prevalence of NCAH presenting as premature pubarche (PP), hirsutism, or polycystic ovarian syndrome (PCOS) and to evaluate the molecular spectrum of CYP21A2 mutations in NCAH patients. Methods. A total of 126 patients (122 females, 4 males) with PP, hirsutism, or PCOS were included in the present study. All patients underwent an ACTH stimulation test. NCAH was considered to be present when the stimulated 17-hydroxyprogesterone plasma level was >10 ng/mL. Results. Seventy-one of the 126 patients (56%) presented with PP, 29 (23%) with PCOS, and 26 (21%) with hirsutism. Six patients (4,7%) were diagnosed with NCAH based on mutational analysis. Four different mutations (Q318X, P30L, V281L, and P453S) were found in six NCAH patients. One patient with NCAH was a compound heterozygote for this mutation, and five were heterozygous. Conclusion. NCAH should be considered as a differential diagnosis in patients presenting with PP, hirsutism, and PCOS, especially in countries in which consanguineous marriages are prevalent.

Genotype-phenotype correlation in 1,507 families with congenital adrenal hyperplasia owing to 21-hydroxylase deficiency

Over the last two decades, we have extensively studied the genetics of congenital adrenal hyperplasia caused by 21-hydroxylase deficiency (CAH) and have performed 8,290 DNA analyses of the CYP21A2 gene on members of 4,857 families at risk for CAH--the largest cohort of CAH patients reported to date. Of the families studied, 1,507 had at least one member affected with one of three known forms of CAH, namely salt wasting, simple virilizing, or nonclassical CAH. Here, we report the genotype and phenotype of each affected patient, as well as the ethnic group and country of origin for each patient. We showed that 21 of 45 genotypes yielded a phenotypic correlation in our patient cohort. In particular, contrary to what is generally reported in the literature, we found that certain mutations, for example, the P30L, I2G, and I172N mutations, yielded different CAH phenotypes. In salt wasting and nonclassical CAH, a phenotype can be attributed to a genotype; however, in simple virilizing CAH, we observe wide phenotypic variability, particularly with the exon 4 I172N mutation. Finally, there was a high frequency of homozygous I2G and V281L mutations in Middle Eastern and Ashkenazi Jewish populations, respectively. By identifying the predominant phenotype for a given genotype, these findings should assist physicians in prenatal diagnosis and genetic counseling of parents who are at risk for having a child with CAH.

A case of congenital adrenal hyperplasia mimicking Cushing's syndrome

Congenital adrenal hyperplasia (CAH) is characterized by decreased adrenal hormone production due to enzymatic defects and subsequent rise of adrenocorticotrophic hormone that stimulates the adrenal cortex to become hyperplastic, and sometimes tumorous. As the pathophysiology is basically a defect in the biosynthesis of cortisol, one may not consider CAH in patients with hypercortisolism. We report a case of a 41-yr-old man with a 4 cm-sized left adrenal tumorous lesion mimicking Cushing's syndrome who was diagnosed with CAH. He had central obesity and acanthosis nigricans involving the axillae together with elevated 24-hr urine cortisol level, supporting the diagnosis of Cushing's syndrome. However, the 24-hr urine cortisol was suppressed by 95% with the low dose dexamethasone suppression test. CAH was suspected based on the history of precocious puberty, short stature and a profound suppression of cortisol production by dexamethasone. CAH was confirmed by a remarkably increased level of serum 17-hydroxyprogesterone level. Gene mutation analysis revealed a compound heterozygote mutation of CYP21A2 (I173N and R357W).

Adrenal disease in pregnancy

Adrenal disorders in pregnancy are relatively rare, yet can lead to significant maternal and fetal morbidity. Making a diagnosis is challenging as pregnancy may alter the manifestation of disease, many signs and symptoms associated with pregnancy are also seen in adrenal disease, and the fetal-placental unit alters the maternal endocrine metabolism and hormonal feedback mechanisms. The most common cause of Cushing's syndrome in pregnancy is an adrenal adenoma, followed by pituitary etiology, adrenal carcinoma, and other exceedingly rare causes. Medical therapy of Cushing's syndrome includes metyrapone and ketoconazole, but generally surgical treatment is more effective. Exogenous corticosteroid administration is the most common cause of adrenal insufficiency, followed by the endogenous causes of ACTH or CRH secretion. Primary adrenal insufficiency is least common. A low early morning cortisol <3 mcg/dL (83 mmol/L) in the non-stressed state and in the setting of typical clinical symptoms confirms the diagnosis. In the second and third trimester cortisol rises to levels 2-3 fold above those in the non-pregnant state, therefore a baseline level of <30 mcg/dL (823 mmol/L) warrants further evaluation. ACTH stimulated normal cortisol values have been established for each trimester. Hydrocortisone, which does not cross the placenta, is the glucocorticoid treatment of choice, and fludrocortisone is used as mineralocorticoid replacement in patients with primary disease. Congenital adrenal hyperplasia is an autosomal recessive disorder; 21-hydroxylase deficiency (21OHD) is the most common form of the disease. Non-classical 21OHD is most common, followed by the salt-wasting and simple virilizing forms. The treatment of choice for pregnant women affected with CAH is hydrocortisone, and fludrocortisones is added for those with the salt-wasting form of the disease. If the fetus is at risk for classical CAH, dexamethasone treatment can be used prenatally to prevent masculinization of the genitalia in a female infant. Because dexamethasone crosses the placenta, it should not be used to treat pregnant women with CAH if the fetus is not at risk for the disease.

Mutation analysis of the CYP21A2 gene in the Iranian population

BACKGROUND

Defects in the CYP21A2 gene cause steroid 21-hydroxylase deficiency, which is the most frequent cause of congenital adrenal hyperplasia. Forty four affected families were investigated to identify the mutation spectrum of the CYP21A2 gene.

METHODS

Families were subjected to clinical, biochemical, and molecular analyses. Allele-specific polymerase chain reaction amplification was used for eight common mutations followed by dosage analysis to exclude CYP21A2 deletions.

RESULTS

The most frequent mutations detected were gene deletions and chimera (31.8%). Other mutation frequencies were as follows: Q318X, 15.9%; I2G, 14.8%; I172N, 5.8%; gene duplication, 5.7%; R356W, 8%; and E6 cluster mutations, 2.3%. Direct sequencing of the CYP21A2 gene revealed R316X, P453S, c.484insT, and a change at the start codon. Different modules carried by patients were classified into five different haplotypes. The genotype phenotype correlation (positive predictive value) for group null, A, B, and C were 92.3%, 85.7%, 100%, and 0, respectively.

CONCLUSIONS

Methods used will be helpful for carrier detection and antenatal diagnosis, especially with inclusion of the multiplex ligation probe dependent amplification technique, which is easier for routine tests in comparison with other methods. Mutation frequencies indicate that Iranians are possible descendants of Asians and Europeans.

Ethnic disparity in 21-hydroxylase gene mutations identified in Pakistani congenital adrenal hyperplasia patients

BACKGROUND

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders caused by defects in the steroid 21 hydroxylase gene (CYP21A2). We studied the spectrum of mutations in CYP21A2 gene in a multi-ethnic population in Pakistan to explore the genetics of CAH.

METHODS

A cross sectional study was conducted for the identification of mutations CYP21A2 and their phenotypic associations in CAH using ARMS-PCR assay.

RESULTS

Overall, 29 patients were analyzed for nine different mutations. The group consisted of two major forms of CAH including 17 salt wasters and 12 simple virilizers. There were 14 phenotypic males and 15 females representing all the major ethnic groups of Pakistan. Parental consanguinity was reported in 65% cases and was equally distributed in the major ethnic groups. Among 58 chromosomes analyzed, mutations were identified in 45 (78.6%) chromosomes. The most frequent mutation was I2 splice (27%) followed by Ile173Asn (26%), Arg 357 Trp (19%), Gln319stop, 16% and Leu308InsT (12%), whereas Val282Leu was not observed in this study. Homozygosity was seen in 44% and heterozygosity in 34% cases. I2 splice mutation was found to be associated with SW in the homozygous. The Ile173Asn mutation was identified in both SW and SV forms. Moreover, Arg357Trp manifested SW in compound heterozygous state.

CONCLUSION

Our study showed that CAH exists in our population with ethnic difference in the prevalence of mutations examined.

Molecular characterization of 25 Chinese pedigrees with 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders mainly caused by a defect in the steroid 21-hydroxylase gene (CYP21A2). In this study, we investigated the molecular defects of 25 Chinese pedigrees with 21-hydroxylase deficiency (21-OHD). Diagnosis of the probands in the families was based on their typical clinical presentations, such as inborn ambiguous genitalia, or early onset of salt wasting and biochemical metabolite abnormalities. All 10 exons and exon-intron boundaries of the CYP21A2 gene were amplified from the genomic DNA of the probands and then analyzed by direct sequencing. The phenotypes of the 26 patients from 25 pedigrees were classified as the classical form of 21-OHD. One novel mutation (c.1223 G>T) and 13 recurrent mutations of CYP21A2 were identified in the 25 pedigrees by genetic analysis. The novel c.1223 G>T mutation results in the substitution of arginine by leucine at amino acid position 408 (p.Arg408Leu). The most frequent mutation alleles were IVS2-13A/C>G (14/52) and I172N (11/52), followed by chimeric mutations (10/52). Forty six of 52 mutated alleles resulted from pseudogene conversion and 6 of 52 from random mutations. The spectrum of CYP21A2 mutation in our study was slightly different from those previously reported in Chinese and in other ethnic groups of the world. Although microconversion events were the main cause of mutations in the CYP21 gene, random mutations with a common origin can also be the reason for 21-OHD.

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency: A paradigm for prenatal diagnosis and treatment

21-Hydroxylase deficiency is the most common cause of congenital adrenal hyperplasia (CAH), an inherited disorder of steroidogenesis. In its severe form, CAH causes genital ambiguity in females. Molecular genetic analysis of fetal DNA obtained by amniocentesis or chorionic villus sampling is used to diagnose steroid 21-OHD deficiency in utero. Large ongoing studies show that appropriate prenatal treatment of pregnant mothers with dexamethasone is effective and safe for both the fetus and the mother. It reduces ambiguous genitalia in the female affected fetus and thus avoids unnecessary genitoplasty in the newborn female.

Multiplex ligation-dependent probe amplification (MLPA) assay for the detection of CYP21A2 gene deletions/duplications in congenital adrenal hyperplasia: first technical report

BACKGROUND

More than 90% of the cases of Congenital Adrenal Hyperplasia (CAH) are associated with mutations in 21-hydroxylase gene (CYP21A2). Up to now, large CYP21A2 rearrangements have been mainly detected by Southern blot analysis, although more rapid methods have been alternatively proposed. In this paper, we report the use of a multiplex ligation-dependent probe amplification (MLPA) method for easy and rapid detection of deletions/duplications in the CYP21A2 gene.

METHODS

We collected 18 CAH Italian patients previously analyzed by gene sequencing and Southern blot technique. In addition, a prenatal diagnosis study was performed.

RESULTS

Of the 7 known subjects with CYP21A2 deletions and 2 with gene duplications previously characterized in our laboratory, all were successfully identified by the MLPA analysis. In the prenatal diagnosis study, the MLPA assay was able to identify the presence of a CYP21A2 gene duplication in the fetus, as well in other two family members.

CONCLUSION

MLPA analysis represents a simple, rapid and sensitive tool for the detection of CYP21A2/CYP21A1P deletions/duplications in CAH molecular diagnosis. Compared to Southern blot, MLPA may be considered a high throughput analysis, allowing the simultaneous study of several samples in the same experiment and the investigation of both gene (CYP21A2) and pseudogene (CYP21A1P) in each patient.

Prenatal diagnosis and treatment of congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) applies to a group of inherited disorders caused by an enzyme deficiency in steroid biosynthesis. The most common form of CAH is 21-hydroxylase deficiency (21-OHD), which in its severe form can cause genital ambiguity in females. Affected females experience virilization both physically and psychologically. Steroid 21-OHD can be diagnosed in utero through molecular genetic analysis of fetal DNA. Appropriate prenatal treatment by dexamethasone administration to the at-risk pregnant mother is effective in reducing genital virilization in the fetus, thus avoiding unnecessary genitoplasty in affected females. Current data from large human studies show that prenatal diagnosis and treatment are safe in the short term for both the fetus and the mother. Preliminary data from long-term studies support these results.

CYP21A2 gene mutations in congenital adrenal hyperplasia: genotype-phenotype correlation in Turkish children

BACKGROUND

Congenital adrenal hyperplasia (CAH) due 21-hydroxylase deficiency (21-OHD) is a common autosomal recessive disorder. It is caused by defects in the CYP21A2 gene.

OBJECTIVE

Our aim was to determine the frequency of common gene mutations and to evaluate genotype-phenotype correlations in Turkish 21-OHD patients.

METHODS

Molecular analysis of the CYP21A2 gene was performed for the detection of the eight most common point mutations [p.P30L, IVS2-13C>G (IVS-2), p.I172N, exon 6 mutation cluster (p.I236N, p.V237E, p.M239K), p.V281L, p.Q318X, p.R356W, 8-bp-deletion], of large deletion and conversion by southern blotting, allele specific semi-quantitative PCR/enzyme restriction method and sequencing, in 56 patients with 21-OHD, from 52 families.

RESULTS

Disease-causing mutations were identified in 77 out of 91 alleles (84.6%) of the patients. Mutations were found in 34 of 43 alleles (79.1%) in salt wasting (SW; n=26), 32 of 36 alleles (88.8%) in simple virilizing (SV; n=24) and 11 of 12 alleles (91.6%) in non-classical (NC; n=6) form of CAH. The most frequent mutations were IVS-2 (22.0%), large conversion (14.3%), p.I172N (9.9%) p.R356W (8.8%), and large deletion (6.6%). In the SW form, the most frequent genotypes were homozygous for IVS-2 (11.5%) and homozygous for large conversion of the gene (11.5%). In the SV form, the most frequent genotype was homozygous for IVS-2 (20%), followed by compound heterozygous for p.I172N/8-bp del (10%). Homozygous for p.V281L (16.7%) was most common in NC. In most cases there was good correlation between genotype and phenotype. In the SW and NC forms, genotypes of all the patients correlated with their phenotypes.

CONCLUSIONS

This is the first comprehensive study on the molecular basis of CAH patients in the Turkish population. Based on these results, we propose a modified screening strategy to facilitate molecular testing of CAH patients in our population.

Identification of frequency and distribution of the nine most frequent mutations among patients with 21-hydroxylase deficiency in Turkey

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders mainly due to defects in the steroid 21-hydroxylase (CYP21A2) gene.

METHODS

To determine the mutational spectrum in the Turkish population, the CYP21A2 active gene was analyzed in 100 unrelated patients with the classical form of 21-hydroxylase deficiency using PCR and RFLP.

RESULTS

Mutations were detected in 78 patients: 64 patients were homozygous for one mutation, seven patients were compound heterozygous with different mutations on each chromosome, two patients were homozygous for two different mutations, five patients were heterozygous, and 22 patients harbored none of the tested mutations. The most frequent mutation was IVS2-13A/C (28.5%), followed by large gene deletion (17%), Q318X (11.5%), I172N (4%), V281L (3.5%), R356W (3.5%), 8-bp (3%), complex alleles (2%), P30L (1%) and E6 cluster (1%).

CONCLUSION

The distribution of mutation frequencies in our study was slightly different from those previously reported in Turkey and in other parts of the world.

Recent advances in diagnosis, treatment, and outcome of congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is an autosomal-recessive disease causing cortisol deficiency, aldosterone deficiency and hyperandrogenism. Diagnosis of 21-OHD is confirmed by steroid analysis in newborn screening or later on. Standard medical treatment consists of oral glucocorticoid and mineralocorticoid administration in order to suppress adrenal androgens and to compensate for adrenal steroid deficiencies. However, available treatment is far from ideal, and not much is known about the long-term outcome in CAH as trials in patients in adulthood or old age are rare. Here we briefly describe the pathophysiology, clinical picture, genetics and epidemiology of 21-OHD. This is followed by a comprehensive review of the recent advances in diagnosis, treatment and outcome. Novel insights have been gained in the fields of newborn screening, specific steroid measurement utilizing mass spectrometry, genetics, glucocorticoid stress dosing, additive medical therapy, prenatal treatment, side-effects of medical treatment, adrenomedullary involvement, metabolic morbidity, fertility and gender identity. However, many issues are still unresolved, and novel questions, which will have to be answered in the future, arise with every new finding.

A simple and robust quantitative PCR assay to determine CYP21A2 gene dose in the diagnosis of 21-hydroxylase deficiency

BACKGROUND

Correct diagnosis of 21-hydroxylase deficiency (21OHD) requires the identification of CYP21A2 gene deletions and CYP21A1P/CYP21A2 chimeric genes, which are disease-causing alleles, and gene duplications, which can lead to false-positive 21OHD allele results. Because lack of suitable CYP21A2 dosage assessment methods hampers correct 21OHD diagnosis, we developed a new assay based on the relative quantification of the CYP21A2 gene using the DSP gene as a reference.

METHODS

The assay to determine CYP21A2 copy number is based on real-time PCR. The method also detects the presence of the CYP21A1P/CYP21A2 chimeric gene. We used a duplex PCR to coamplify the DSP gene, included as an internal control, along with CYP21A2. The difference in threshold cycles between CYP21A2 and DSP genes (DeltaCt) was used to assess CYP21A2 copy number.

RESULTS

The DeltaCt values obtained from 24 samples used to set up the method clearly differentiated 3 nonoverlapping intervals, which corresponded to the number of CYP21A2 copies: -1.35 to -0.25 defined 2 gene copies, +0.20 to +2.00 defined 1 copy, and -2.50 to -1.50 defined 3 copies. With these intervals we were able to assess the gene copy number in 24 additional samples.

CONCLUSIONS

This new method for gene copy assessment detects homozygous and heterozygous CYP21A2 gene deletions, CYP21A1P/CYP21A2 chimeric genes, and gene duplications. Moreover, the method is robust, fast, and easy to use in a molecular diagnosis laboratory. This method together with CYP21A2 gene sequencing can provide a definitive system for the detection of almost all, common as well as rare, 21OHD alleles.

Prenatal diagnosis and treatment of congenital adrenal hyperplasia owing to 21-hydroxylase deficiency

Classical forms of congenital adrenal hyperplasia are caused by a severe deficiency of 21-hydroxylase, an enzyme involved in steroid biosynthesis, which triggers excessive androgen production before birth. Affected females experience virilization both physically and psychologically. Prenatal diagnosis and treatment of congenital adrenal hyperplasia has been implemented for more than 20 years. In utero gene-specific diagnosis is now feasible for fetal cell samples derived from chorionic villi or amniotic cells in culture, and this gene-specific diagnosis guides the treatment of the affected female fetus. Appropriate dexamethasone administration to the at-risk pregnant mother is effective in reducing genital virilization in the fetus, and thus avoids unnecessary genitoplasty in affected females. Current data from large human studies show the benefit and safety of prenatal treatment. Long-term follow-up of the safety of prenatal treatment is currently underway. This practice is a rare example of effective prenatal treatment to prevent a malformation caused by an inborn error of metabolism.

Congenital adrenal hyperplasia: focus on the molecular basis of 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused by defects in one of several steroidogenic enzymes involved in the synthesis of cortisol from cholesterol in the adrenal glands. More than 90% of cases are caused by 21-hydroxylase deficiency, and the severity of the resulting clinical symptoms varies according to the level of 21-hydroxylase activity. 21-Hydroxylase deficiency is usually caused by mutations in theCYP21A2gene, which is located on the RCCX module, a chromosomal region highly prone to genetic recombination events that can result in a wide variety of complex rearrangements, such as gene duplications, gross deletions and gene conversions of variable extensions. Molecular genotyping ofCYP21A2and the RCCX module has proved useful for a more accurate diagnosis of the disease, and prenatal diagnosis. This article summarises the clinical features of 21-hydroxylase deficiency, explains current understanding of the disease at the molecular level, and highlights recent developments, particularly in diagnosis.

Ethnic-specific distribution of mutations in 716 patients with congenital adrenal hyperplasia owing to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) occurs worldwide. The most common mutations in the CYP21A2 gene in 716 unrelated patients were analyzed and the mutations were grouped by ethnicity, as defined through self-declaration corroborated by review of pedigrees extending to two or three generations. Prevalent allelic mutations and genotypes were found to vary significantly among ethnic groups, and the predominance of the prevalent mutations and genotypes in several of these populations was significant. There are ethnic-specific mutations in the CYP21A2 gene. A large deletion is prevalent in the Anglo-Saxons; a V281L (1685 G to T) mutation is prevalent in Ashkenazi Jews; an R356W (2109 G to A) mutation is prevalent in the Croatians; an IVS2 AS -13 (A/C to G) mutation is prevalent in the Iranians and Yupik-speaking Eskimos of Western Alaska; and a Q318X (1994 C to T) mutation is prevalent in East Indians. Genotype/phenotype non-correlation was seen when at least one IVS2 AS -13 (A/C to G) mutation in the CYP21A2 gene was present.

Aldosterone-to-renin ratio as a marker for disease severity in 21-hydroxylase deficiency congenital adrenal hyperplasia

CONTEXT

Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency (21 OHD) is classified clinically in decreasing order of severity into salt-wasting, simple-virilizing, and nonclassical forms. Causative mutations in the CYP21A2 gene dictate the degrees of adrenal enzyme defect. Salt-wasting crises due to aldosterone deficiency are clinically apparent in the salt-wasting form but not in other forms of 21 OHD.

OBJECTIVES

This study examined the ratio of serum aldosterone to plasma renin activity as an index of sodium wasting in patients with 21 OHD CAH, heterozygotes, and normal individuals.

DESIGN

This was a cross-sectional, retrospective, noninterventional study.

PATIENTS AND OTHER PARTICIPANTS

A total of 402 individuals were included: 224 patients affected with 21 OHD CAH and 178 unaffected subjects. Classification into each diagnostic group was made primarily on the basis of clinical and hormonal features. Affected or unaffected status was confirmed by genotype of CYP21A2. All subjects were on ad lib diets without restrictions. Salt-wasting status was examined by sodium deprivation testing in 32 salt-wasting subjects and 14 simple virilizing subjects.

RESULTS

The ratio of serum aldosterone to plasma renin activity was found to discriminate well between the different groups of disease severity. The lowest ratios, indicative of the least sodium conservation, were seen in the salt-wasting group with increasing ratios in the simple virilizing, nonclassical, and unaffected groups. This ratio remained stable with age.

CONCLUSION

The ratio of serum aldosterone to plasma renin activity provides a simple index to compare groups of patients with varying degrees of 21 OHD.

Extensive clinical experience: nonclassical 21-hydroxylase deficiency

CONTEXT

Nonclassical congenital adrenal hyperplasia (CAH) owing to steroid 21-hydroxylase deficiency (NC21OHD) is the most frequent of all autosomal recessive genetic diseases, occurring in one in 100 persons in the heterogeneous New York City population. NC21OHD occurs with increased frequency in certain ethnic groups, such as Ashkenazi Jews, in whom one in 27 express the disease. NC21OHD is underdiagnosed in both male and female patients with hyperandrogenic symptoms because hormonal abnormalities in NC21OHD are only mild to moderate, not severe as in the classical form of CAH. Unlike classical CAH, NC21OHD is not associated with ambiguous genitalia of the newborn female.

MAIN OUTCOME MEASURES

The hyperandrogenic symptoms include advanced bone age, early pubic hair, precocious puberty, tall stature, and early arrest of growth in children; infertility, cystic acne, and short stature in both adult males and females; hirsutism, frontal balding, polycystic ovaries, and irregular menstrual periods in females; and testicular adrenal rest tissue in males.

CONCLUSIONS

The signs and symptoms of hyperandrogenism are reversed with dexamethasone treatment.

Prenatal diagnosis and treatment of congenital adrenal hyperplasia

Congenital adrenal hyperplasia is a group of inherited disorders caused by an enzyme deficiency in steroid biosynthesis. The most common form of congenital adrenal hyperplasia is 21-hydroxylase deficiency, which in its severe form can cause genital ambiguity in females. Steroid 21-hydroxylase deficiency can be diagnosed in utero through molecular genetic analysis of fetal DNA. Prenatal treatment successfully reduces genital ambiguity, and the subsequent problems of sex misassignment and gender confusion. Data from current studies show that prenatal diagnosis and treatment are safe for the mother and the fetus. The evidence also suggests that it is safe over the long term, but all subjects exposed to dexamethasone treatment during embryonic and fetal life should have their physical, cognitive and emotional developments recorded.

Diagnosis and management of congenital adrenal hyperplasia

Congenital adrenal hyperplasia is the name applied to a class of autosomal recessive disorders resulting from deficiency of one of five enzymes necessary for cortisol synthesis by the adrenal cortex. Congenital adrenal hyperplasia is most often attributable to steroid 21-hydroxylase deficiency, accounting for more than 90% of cases. This discussion will be limited to the most common form of the disease, highlighting methods of diagnostic screening and challenges in disease management.

Validation and clinical application of a locus-specific polymerase chain reaction- and minisequencing-based assay for congenital adrenal hyperplasia (21-hydroxylase deficiency)

Congenital adrenal hyperplasia is an autosomal recessive disorder caused by defective adrenal steroid biosynthesis, resulting in reduced glucocorticoid and increased androgen production. The majority of cases are due to inactivation of the 21-hydroxylase gene (CYP21A2), most commonly caused by genomic rearrangements with the adjacent, highly homologous pseudogene CYP21A. The most common deletions and gene conversion events have been defined and are typically detected by Southern hybridization detection of CYP21 rearrangements and/or polymerase chain reaction (PCR). However, Southern hybridization is laborious, and allele-specific PCR results may be difficult to interpret. We have therefore developed a locus-specific, PCR-based, minisequencing method for detecting the 12 most common CYP21A2 mutations. We validated the assay using a panel of 20 previously genotyped samples obtained from individuals who collectively have a broad spectrum of mutations causing 21-hydroxylase deficiency. We also used 19 control samples having no CYP21 mutations. All validation samples were correctly typed, and we identified haplotypes that may be useful for clinical diagnosis. Results from 102 clinical samples demonstrate that this assay is a rapid, reliable, and robust method for locus-specific identification of mutations and is suitable for routine clinical use and prenatal diagnosis.

Substitutions in the CYP21A2 promoter explain the simple-virilizing form of 21-hydroxylase deficiency in patients harbouring a P30L mutation

The classical and nonclassical phenotypes of 21-hydroxylase deficiency represent a continuous spectrum of the impairment of 21-hydroxylase activity due to mutations between the CYP21A2 gene. These mutations occur mainly by microconversion in the homologous nonfunctional CYP21A1P gene. The P30L mutation is associated with the nonclassical form, and it reduces the activity to 30-40% of the normal enzyme. We have described three female patients exhibiting a simple virilizing phenotype and bearing the P30L mutation in compound heterozygosis with a severe mutation. To identify additional mutations causing this phenotype, the promoter region was sequenced and four mutations were identified: -126C --> T, -113G --> A, -110T --> C and -103 A --> G. These substitutions are normally present in the promoter region of the pseudogene and in vitro studies demonstrated that they reduced the transcriptional activity fivefold. They might have been converted to the CYP21A2 promoter together with the P30L mutation in these patients. Therefore, these substitutions in synergism with the P30L mutation might decrease the enzyme activity resulting in a more severe phenotype, and a DNA sequence of -167 bases of the CYP21A2 gene should be performed in patients with 21-hydroxylase deficiency in whom the phenotype is more severe than predicted by the genotype.