Novel and prevalent CYP11B1 gene mutations in Turkish patients with 11-β hydroxylase deficiency

Targeted long-read sequencing identifies missing pathogenic variant in unsolved 11β-hydroxylase deficiency

BACKGROUND

11β-hydroxylase deficiency (11β-OHD), caused by homozygosity or compound heterozygosity CYP11B1 variants, is the second most common cause of congenital adrenal hyperplasia (CAH). Due to the high degree of sequence identity between CYP11B1 and CYP11B2, chimeric genes, and complex structural variants (SVs), the conventional approach to gene testing for 11β-OHD is facing challenges. The study aimed to clarify the underlying genetic causes of two siblings of a Chinese family with 11β-OHD.

METHODS

Peripheral blood samples and clinical information were collected from subjects and their family members. Sex steroid concentrations were measured using LC-MS/MS. Long-range PCR-based next-generation sequencing (NGS), PCR assay and target long-read sequencing were used to detect the pathogenic variants.

RESULTS

Early onset hypertension, increased serum levels of adrenocorticotropin (ACTH), progesterone, testosterone, and decreased cortisol and potassium were detected in both affected siblings. Long-range PCR-based NGS identified a heterozygous missense variant (NM_000497.4:c.281 C > T, p.P94> L) in CYP11B1 gene in the two siblings. PCR detected no chimeric CYP11B2/CYP11B1 gene. We finally identified a second pathogenic variant in CYP11B1 gene via target long-read sequencing (T-LRS). This novel variant was a deletion-insertion variant and located chr8:143957269-143,957,579 (hg19) with the insertion of 'ACAG' (NM_000497.4:c.954 + 78_980delinsACAG), which was in trans with CYP11B1: c.281 C > T.

CONCLUSIONS

Our study suggests that the integrated long-range PCR-based NGS and T-LRS seem to be the most reliable and accurate method for 11β-OHD genetic diagnosis and carrier sequencing.

Identification and functional characterization of compound heterozygous CYP11B1 gene mutations

PURPOSE

11β-Hydroxylase deficiency (11β-OHD) is the second leading cause of congenital adrenal hyperplasia (CAH), a rare autosomal recessive disease caused by mutations in the CYP11B1 gene. We previously reported the case of a male Chinese patient with typical 11β-OHD symptoms. Sanger sequencing revealed that the patient carried a splice-site mutation, c.595+1G>A in the CYP11B1 gene. His mother and sister harbored the heterozygous mutation, c.595+1G>A. Paradoxically, Sanger sequencing did not detect any abnormality in the CYP11B1 gene of his father and brother. Therefore, in this study, we aimed to further explore the exact genetic etiology of 11β-OHD in this pedigree and analyze the functional consequence of the c.595+1G>A mutation.

METHODS

Gemomic DNA was extracted from the peripheral blood leukocytes of the family members and normal control individuals, followed by quantitative real-time polymerase chain reaction (qPCR) to detect the copy number of the target CYP11B1 gene fragment. Mutation analysis was also performed via whole-exome sequencing (WES) followed by Sanger sequencing validation. In vitro minigene assay was also performed to investigate the impact of the c.595+1G>A mutation on pre-mRNA splicing.

RESULTS

qPCR results suggested a heterozygous deletion encompassing position c.595+1 along with flanking exonic and intronic sequences in the CYP11B1 gene of the patient and his father. WES followed by Sanger sequencing verified that the patient carried compound heterozygous mutations in the CYP11B1 gene, including a novel 2840-bp deletion (c.395+661_c.1121+180del) and c.595+1G>A, while his father carried the heterozygous c.395+661_c.1121+180del mutation. No other novel CYP11B1 mutations were found in the rest of the family members. Furthermore, minigene assay revealed that the c.595+1G>A mutation resulted in a 70-bp deletion of exon 3 in the mRNA, and this altered the reading frame at amino acid 176 and created a premature stop codon at amino acid 197.

CONCLUSION

We identified a novel 2840-bp-sized large deletion and confirmed that the c.595+1G>A mutation disrupts normal pre-mRNA splicing. Either mutation could significantly alter the reading frame and abolish CYP11B1 enzyme activity. Therefore, our findings widen the mutation spectrum of CYP11B1 and provide an accurate diagnosis of 11β-OHD at a molecular genetic level.

Chimeric Genes Causing 11β-Hydroxylase Deficiency: Implications in Clinical and Molecular Diagnosis

Deficiency of 11β-hydroxylase (11β-OHD) is the second most common cause of congenital adrenal hyperplasia (CAH), accounting for 0.2-8% of all cases. The disease is transmitted as an autosomal recessive trait and the underlying genetic causes of 11β-OHD are primarily small pathogenic variants affecting the CYP11B1 gene coding the 11β-hydroxylase enzyme. However, special events complicate the molecular diagnosis of 11β-OHD such as an unequal crossing over between the CYP11B2 (coding aldosterone synthase enzyme) and CYP11B1 genes. The resulting allele contains a hybrid gene, with a CYP11B2 5'-end and a CYP11B1 3'-end, where the CYP11B1 gene is under the control of the CYP11B2 promoter and thus not responding to the adrenocorticotropin (ACTH) but to angiotensin II and K+. This leads a reduction of cortisol production in 11β-OHD. In particular, CYP11B2/CYP11B1 chimeric genes can be distinguished into two groups depending on the breakpoint site: chimeras with breakpoint after the exon 5 of CYP11B2 preserve the aldosterone synthase activity, the others with breakpoint before exon 5 lose this function. In the last case, a more severe phenotype is expected. The aim of this review was to explore the setting of CYP11B2/CYP11B1 chimeras in 11β-OHD, performing a careful review of clinical literature cases.

Molecular analysis of 12 Chinese patients with 11β-hydroxylase deficiency and in vitro functional study of 20 CYP11B1 missense variants

Steroid 11β-hydroxylase deficiency (11β-OHD) is a rare autosomal recessive disorder caused by pathogenic variants of CYP11B1 gene. This study aimed to perform molecular analysis of a Chinese 11β-OHD series and in vitro functional study of twenty CYP11B1 missense variants. Twelve Chinese patients with clinical diagnosis of 11β-OHD were included in the study to analyze their molecular etiology. Genomic DNA of patients was extracted to be sequenced all coding exons and intronic flanking sequences of CYP11B1. Fourteen missense variants found in 12 patients mentioned above along with 6 missense variants previously reported by our team were evaluated functionally. Amino acid substitutions were analyzed with computational program to determine their effects on the three-dimensional structure of CYP11B1 protein. Clinical characteristics and hormone levels at baseline of the 18 patients carrying 18 missense variants aforementioned were recorded to perform genotype-phenotype correlation. A total of 21 rare variants including 9 novel and 12 recurrent ones were identified in 12 patients, out of which 17 were missense, 2 were nonsense, 1 was a splice site variant, and 1 was a deletion-insertion variant. Results of in vitro functional study revealed that 3 out of 20 missense mutants (p.Leu3Pro, p.Gly267Ser, and p.Ala367Ser) had partial enzyme activity and the other 17 had little enzymatic activity. The impairment degree of enzymatic activity in vitro functional study was also reflected in the severity degree of interaction change between the wild-type/mutant-type amino acid and its adjacent amino acids in three-dimensional model. In conclusion, the addition of 9 novel variants expands the spectrum of CYP11B1 pathogenic variants. Our results demonstrate that twenty CYP11B1 variants lead to impaired 11β-hydroxylase activity in vitro. Visualizing these variants in the three-dimensional model structure of CYP11B1 protein can provide a plausible explanation for the results measured in vitro.

A Novel Homozygous Pathogenic Variant in CYP11B1 in a Female Iranian Patient with 11B Hydroxylase Deficiency

Objective

Congenital adrenal hyperplasia (CAH) addresses a number of autosomal recessive disorders characterized by the enzyme defects in steroid hormones biosynthesis. The second common form of CAH is caused by mutations in the CYP11B1 gene. Here, we reveal a novel mutation in the CYP11B1 gene related to the 11βOHD phenotype.

Methods and Results

Sequence analysis of the CYP11B1 gene in a 19-year-old Iranian woman with the 11βOHD phenotype was performed. In silico analysis and molecular docking were done. A novel missense homozygous variant c.1351C > T (p.L451F) in the CYP11B1 gene was identified in the patient and, according to American College of Medical Genetics and Genomics criteria, was categorized as likely pathogenic. Protein docking showed destructive effects of the variant on the CYP11B1 protein-ligand interactions.

Conclusion

This study broadens the CYP11B1 mutation spectrum and introduces the novel p.L451F likely pathogenic variant leading to destructive effects on protein-ligand interactions. Our results provide reliable information for genetic counseling and molecular diagnostics of CAH.

Congenital adrenal hyperplasia caused by compound heterozygosity of two novel CYP11B1 gene variants

BACKGROUND

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused by pathogenic variants in seven genes involved in the cortisol and aldosterone biosynthetic pathway. The second most common cause, 11β-hydroxylase deficiency (11βOHD), is attributed to pathogenic variants in the CYP11B1 gene encoding for the enzyme 11β-hydroxylase (11βOH).

CASE PRESENTATION

A 13-year-old girl was referred to the pediatric endocrinologist due to a syncopal episode. She is the third child of non-consanguineous parents. She presented with premature adrenarche at the age of 6 years and menarche at the age of 12 years. On physical examination, her height was 154.5 cm and weight 50 kg, while she presented with acne, hirsutism, clitoromegaly, and normal blood pressure. Laboratory investigation revealed increased androgen levels and poor cortisol response to the ACTH stimulation test. From the family history, the mother was diagnosed with CAH at the age of 10 years and was under treatment with methylprednisolone. Previous molecular investigation of the CYP21A2 gene was negative. Due to the increased androstenedione levels in the index patient, the suspicion of 11βOH was raised, and she was investigated for 11-deoxycortisol, 11-deoxycorticosterone, and CYP11B1 gene pathogenic variants. The patient and her mother were found to be compound heterozygous for two novel variants of the CYP11B1 gene.

CONCLUSION

We present a case of CAH due to compound heterozygosity of two novel pathogenic variants of the CYP11B1 gene, emphasizing the importance of molecular investigation in order to confirm clinical diagnosis and allow proper genetic counseling of the family.

Classical 11β-Hydroxylase Deficiency Caused by a Novel Homozygous Mutation: A Case Study and Literature Review

Congenital adrenal hyperplasia (CAH) is an uncommon condition and 11β-hydroxylase deficiency (11βOHD) accounts for 0.2-8% of cases. In this study, we report a three-year-old girl with a known diagnosis of classical CAH on maintenance treatment with hydrocortisone who presented with abnormal genitalia and persistent hypertension. Genetic testing confirmed the diagnosis of autosomal recessive CAH due to 11βOHD as a result of a novel homozygous pathogenic mutation, c.53dup p.(Gln19Alafs*21), in the CYP11B1 gene. Physicians should consider the possibility of classical 11βOHD in CAH patients presenting with persistent hypertension, even if other laboratory biomarkers are equivocal.

Clinical and Hormonal Profiles Correlate With Molecular Characteristics in Patients With 11β-Hydroxylase Deficiency

BACKGROUND

Given the rarity of 11β-hydroxylase deficiency (11βOHD), there is a paucity of data about the differences in clinical and biochemical characteristics of classic (C-11βOHD) and nonclassic 11βOHD (NC-11βOHD).

OBJECTIVE

To characterize a multicenter pediatric cohort with 11βOHD.

METHOD

The clinical and biochemical characteristics were retrospectively retrieved. CYP11B1 gene sequencing was performed. Seventeen plasma steroids were quantified by liquid chromatography-mass spectrometry and compared to that of controls.

RESULTS

102 patients (C-11βOHD, n = 92; NC-11βOHD, n = 10) from 76 families (46,XX; n = 53) had biallelic CYP11B1 mutations (novel 9 out of 30). Five 46,XX patients (10%) were raised as males. Nineteen patients (19%) had initially been misdiagnosed with 21-hydroxylase deficiency. Female adult height was 152 cm [-1.85 SD score (SDS)] and male 160.4 cm (-2.56 SDS).None of the NC-11βOHD girls had ambiguous genitalia (C-11βOHD 100%), and none of the NC-11βOHD patients were hypertensive (C-11βOHD 50%). Compared to NC-11βOHD, C-11βOHD patients were diagnosed earlier (1.33 vs 6.9 years; P < 0.0001), had higher bone age-to-chronological age (P = 0.04) and lower adult height (-2.46 vs -1.32 SDS; P = 0.05). The concentrations of 11-oxygenated androgens and 21-deoxycortisol were low in all patients. The baseline ACTH and stimulated cortisol were normal in NC-11βOHD. Baseline cortisol; cortisone; 11-deoxycortisol; 11-deoxycorticosterone and corticosterone concentrations; and 11-deoxycortisol/cortisol, 11-deoxycorticosterone/cortisol, and androstenedione/cortisol ratios were higher in C-11βOHD than NC-11βOHD patients (P < 0.05). The 11-deoxycortisol/cortisol ratio >2.2, <1.5, and <0.1 had 100% specificity to segregate C-11βOHD, NC-11βOHD, and control groups.

CONCLUSION

NC-11βOHD can escape from clinical attention due to relatively mild clinical presentation. However, steroid profiles enable the diagnosis, differential diagnosis, and subtyping of 11βOHD.

Compound heterozygosity of a novel Q73X mutation and a known R141X mutation in CYP11B1 resulting in 11β-hydroxylase deficiency in a Chinese boy with congenital adrenal hyperplasia

Steroid 11β-hydroxylase deficiency (11β-OHD), which is caused by mutations of the CYP11B1 gene, is the second leading cause of congenital adrenal hyperplasia (CAH), an autosomal recessive inherited disorder. Here, we report a case of classic 11β-OHD in a Chinese boy characterized by hypertension, penile enlargement, skin pigmentation, and acne. Molecular analysis of CYP11B1 revealed that the patient was compound heterozygous for a c.217C > T (p.Q73X) mutation in exon 1 and a c.421C > T (p.R141X) mutation in exon 3. His parents carried the novel c.217C > T (p.Q73X) mutation and the prevalent c.421C > T (p.R141X) mutation. Furthermore, we identified a novel 217-bp substitution mutation (Q73X) in CYP11B1 that generates a truncated protein without biological activity, which is likely to be pathogenic. Pursuant to the phenotype of the proband and his family, the Q73X mutation is inferred to exacerbate the disease burden of the R141X mutation, a known pathogenic variant. To further explore this possibility, selecting the x-ray structure of human CYP11B2 as a template, we built three-dimensional homologous models of the normal and mutant proteins. In the mutant model, a change from a helix to terminal structure in amino acids 73 and 141 occurred that affected the binding capacity of CYP11B1 with heme and impaired 11β-hydroxylase activity. Taken together, our findings expand the spectrum of known mutations leading to 11β-OHD and provide evidence to study genotype-phenotype concordance, confirm early diagnosis and treatment of 11β-OHD, and prevent most complications.

Clinical and Molecular Analysis of Four Patients With 11β-Hydroxylase Deficiency

Objective: 11β-hydroxylase deficiency (11βOHD) is a rare autosomal recessive disorder caused by mutations in the CYP11B1 gene. It is characterized by virilization, hypertension, and significant final height impairment. In this study, we aim to investigate the clinical and molecular characteristics of four unrelated Chinese patients with 11βOHD disorder. Methods: The clinical information of four 11βOHD patients were carefully reviewed. Genetic analysis was performed using next-generation sequencing (NGS) based panel analysis. NGS coverage depth was analyzed to detect exonic copy-number variants (CNVs) on patient 1. Quantitative PCR (qPCR) was subsequently performed to confirm the CNVs detected from the NGS coverage depth analysis. Results: The mean age of the patients at diagnosis was 4.7 years (range, 2.0-9.3 years). Two genetically female patients (patients 1 and 2) with 11βOHD presented severe virilization of external genitalia and were raised as males. Two genetically male patients (patients 3 and 4) presented precocious puberty. Additionally, patients 1, 3, and 4 presented with hypertension. In patient 4, unilateral adrenal mass was detected and removed at the age of 9 years. Interestingly, the height of patient 4 (174.4 cm, +6.7 SD) wasn't impaired and reached his mid-parental height (173 cm). Three novel variants in the CYP11B1 gene (c.1150_1153del, c.217C>T, and c.400G>C) were identified by NGS. Various bioinformatics tools revealed potential pathogenic effects for the novel variants, and evolutionary-conservation revealed that the novel missense variant affected an amino acid that is highly conserved among species. Furthermore, NGS coverage depth analysis and qPCR identified a novel heterozygous deletion of exons 1-6 in patient 1. Conclusion: Our study expands the spectrum of mutations of the CYP11B1 gene in Chinese population. In addition, We reported the first case of a patient with classical 11βOHD disorder, whose final height wasn't compromised.

46,XX DSD due to Androgen Excess in Monogenic Disorders of Steroidogenesis: Genetic, Biochemical, and Clinical Features

The term 'differences of sex development' (DSD) refers to a group of congenital conditions that are associated with atypical development of chromosomal, gonadal, or anatomical sex. Disorders of steroidogenesis comprise autosomal recessive conditions that affect adrenal and gonadal enzymes and are responsible for some conditions of 46,XX DSD where hyperandrogenism interferes with chromosomal and gonadal sex development. Congenital adrenal hyperplasias (CAHs) are disorders of steroidogenesis that mainly involve the adrenals (21-hydroxylase and 11-hydroxylase deficiencies) and sometimes the gonads (3-beta-hydroxysteroidodehydrogenase and P450-oxidoreductase); in contrast, aromatase deficiency mainly involves the steroidogenetic activity of the gonads. This review describes the main genetic, biochemical, and clinical features that apply to the abovementioned conditions. The activities of the steroidogenetic enzymes are modulated by post-translational modifications and cofactors, particularly electron-donating redox partners. The incidences of the rare forms of CAH vary with ethnicity and geography. The elucidation of the precise roles of these enzymes and cofactors has been significantly facilitated by the identification of the genetic bases of rare disorders of steroidogenesis. Understanding steroidogenesis is important to our comprehension of differences in sexual development and other processes that are related to human reproduction and fertility, particularly those that involve androgen excess as consequence of their impairment.

Neonatal Screening for Congenital Adrenal Hyperplasia in Turkey: A Pilot Study with 38,935 Infants

Objective

Congenital adrenal hyperplasia (CAH) is the most common form of primary adrenal insufficiency in children. Neonatal screening for CAH is effective in detecting the salt-wasting (SW) form and in reducing mortality. In this study, our aim was to estimate the incidence of CAH in Turkey and to assess the characteristics and efficacy of the adopted newborn CAH screening strategy.

Methods

A pilot newborn CAH screening study was carried out under the authority of the Turkish Directorate of Public Health. Newborn babies of ≥32 gestational weeks and ≥1500 gr birth weight from four cities, born between March 27-September 15, 2017 were included in the study. Screening protocol included one sample two-tier testing. In the first step, 17α-hydroxyprogesterone (17-OHP) was measured by fluoroimmunoassay in dried blood spots (DBS) obtained at 3-5 days of life. The cases with positive initial screening were tested by steroid profiling in DBS using a liquid chromatography-tandem mass spectrometry method to measure 17-OHP, 21-deoxycortisol (21-S), cortisol (F), 11-deoxycortisol and androstenedione as a second-tier test. The babies with a steroid ratio (21-S+17-OHP)/F of ≥0.5 were referred to pediatric endocrinology clinics for diagnostic assessment.

Results

38,935 infants were tested, 2265 (5.82%) required second-tier testing and 212 (0.54%) were referred for clinical assessment, six of whom were diagnosed with CAH (four males, two females). Four cases were identified as SW 21-hydroxylase deficiency (21-OHD) (two males, two females). One male baby had simple virilizing 21-OHD and one male baby had 11-OHD CAH. The incidence of classical 21-OHD in the screened population was 1:7,787.

Conclusion

The incidence of CAH due to classical 21-OHD is higher in Turkey compared to previous reports. We, therefore, suggest that CAH be added to the newborn screening panel in Turkey. The use of steroid profiling as a second-tier test was found to improve the efficacy of the screening and reduce the number of false-positives.

Long-term follow-up of a female patient with non-classical 11β-hydroxylase deficiency and two novel mutations in CYP11B1

11β-Hydroxylase deficiency is the second most common enzyme disorder after 21-hydroxylase deficiency causing congenital adrenal hyperplasia (CAH_11β). In females, the clinical phenotype of CAH_11β classic forms is associated with ambiguous genitalia, virilization and hypertension, while most common complaints in milder non-classic forms include hirsutism, acne, menstrual disturbances, and infertility. Herein, we present clinical and genetic characteristics of an adult woman with 11β-hydroxylase deficiency, hypertension and infertility; she has been followed up from her first pregnancy to her early menopause. Genetic analyses of the patient revealed a compound-heterozygosity due to two variants in the CYP11B1 gene p.Val316Met and p.Asp480ThrfsTer2. Both mutations have not been previously reported as pathogenic in the literature. Emerging questions concerning the clinical management, fertility potential, mineral corticoid abnormalities and perimenopausal transition in patients with non-classic CAH_11β have also been briefly discussed. The presented case of an adult woman with CAH_11β shows that the proper diagnosis and close monitoring of patients with different CAH forms might ensure good therapy adherence and successful fertility.

MECHANISMS IN ENDOCRINOLOGY: Rare defects in adrenal steroidogenesis

Congenital adrenal hyperplasia (CAH) is a group of genetic disorders of adrenal steroidogenesis that impair cortisol synthesis, with compensatory increases in ACTH leading to hyperplastic adrenals. The term 'CAH' is generally used to mean 'steroid 21-hydroxylase deficiency' (21OHD) as 21OHD accounts for about 95% of CAH in most populations; the incidences of the rare forms of CAH vary with ethnicity and geography. These forms of CAH are easily understood on the basis of the biochemistry of steroidogenesis. Defects in the steroidogenic acute regulatory protein, StAR, disrupt all steroidogenesis and are the second-most common form of CAH in Japan and Korea; very rare defects in the cholesterol side-chain cleavage enzyme, P450scc, are clinically indistinguishable from StAR defects. Defects in 3β-hydroxysteroid dehydrogenase, which also causes disordered sexual development, were once thought to be fairly common, but genetic analyses show that steroid measurements are generally unreliable for this disorder. Defects in 17-hydroxylase/17,20-lyase ablate synthesis of sex steroids and also cause mineralocorticoid hypertension; these are common in Brazil and in China. Isolated 17,20-lyase deficiency can be caused by rare mutations in at least three different proteins. P450 oxidoreductase (POR) is a co-factor used by 21-hydroxylase, 17-hydroxylase/17,20-lyase and aromatase; various POR defects, found in different populations, affect these enzymes differently. 11-Hydroxylase deficiency is the second-most common form of CAH in European populations but the retention of aldosterone synthesis distinguishes it from 21OHD. Aldosterone synthase deficiency is a rare salt-losing disorder. Mild, 'non-classic' defects in all of these factors have been described. Both the severe and non-classic disorders can be treated if recognized.

Prevalence, clinical characteristics and long-term outcomes of classical 11 β-hydroxylase deficiency (11BOHD) in Turkish population and novel mutations in CYP11B1 gene

Congenital adrenal hyperplasia (CAH) due to 11β-hydroxylase deficiency (11BOHD) is a rare autosomal recessive disorder and the second most common form of CAH.

AIM

To investigate genotype-phenotype correlation and to evaluate clinical characteristics and long-term outcomes of patients with 11BOHD.

METHODS

A total of 28 patients (n = 14, 46,XX; n = 14, 46,XY) with classical 11BOHD from 25 unrelated families were included in this study. Screening of CYP11B1 is performed by Sanger sequencing. Pathogenic features of novel variants are investigated by the use of multiple in silico prediction tools and with family based co-segregation studies. Protein simulations were investigated for two novel coding region alterations.

RESULTS

The age at diagnosis ranged from 6 days to 12.5 years. Male patients received diagnose at older ages than female patients. The rate of consanguinity was high (71.4%). Five out of nine 46,XX patients were diagnosed late (age 2-8.7 years) and were assigned as male due to severe masculinization. Twenty one patients have reached adult height and sixteen were ultimately short due to delayed diagnosis. Two male patients had testicular microlithiasis and 5 (35.7%) patients had testicular adrenal rest tumor during follow up. Four patients (28.6%) had gynecomastia. Mutation analyses in 25 index patients revealed thirteen different mutations in CYP11B1 gene, 4 of which were novel (c.393 + 3A > G, c.428G > C, c.1398 + 2T > A, c.1449_1451delGGT). The most frequent mutations were c.896T > C with 32%, c.954G > A with 16% and c.1179_1180dupGA with 12% in frequency. There was not a good correlation between genotype and phenotype; phenotypic variability was observed among the patients with same mutation.

CONCLUSION

This study presents the high allelic heterogeneity of CYP11B1 mutations in CAH patients from Turkey. Three dimensional protein simulations may provide additional support for the pathogenicity of the genetic alterations. Our results provide reliable information for genetic counseling, preventive and therapeutic strategies for the families.

Two rare forms of congenital adrenal hyperplasia, 11β hydroxylase deficiency and 17-hydroxylase/17,20-lyase deficiency, presenting with novel mutations

BACKGROUND

Congenital adrenal hyperplasia (CAH) is a rare autosomal recessive disorder caused by deficiency of various enzymes responsible for adrenal steroidogenesis. 11-Beta-hydroxylase deficiency (11βOHD) and 17-hydroxylase/17,20-lyase deficiency (17OHD) are rare causes of CAH.

METHODS/RESULTS

We hereby present a 65-year-old man with 11βOHD and a 33-year-old woman with 17OHD. The man with 11βOHD presented with peripheral precocious puberty and hypertension at age 15 years, fathered two children but developed complications of chronic glucocorticoid therapy on long-term follow-up. Interestingly, his younger sister had been diagnosed with the same condition at age 19 and had later given birth to four children while on glucocorticoids. Exome sequencing of the CYP11B1 gene detected the previously reported pathogenic mutation T318T (c.954G > A [p.Thr318Thr]) on one of the alleles and a novel mutation, R123G (c.367C > G [p.Arg123Gly]), on the other in a highly conserved region of the CYP11B1 gene. The woman with 17OHD presented with severe hypokalemia at age 22 years against a background of primary amenorrhea and lack of development of secondary sexual characteristics. She was heterozygous for a previously recognized mutation, R125Q (c.374G > A [p.Arg125Gln]), and a novel single base-pair deletion, G337fs (c.1010delG [p.Gly337Valfs*82]), which creates a frameshift with a new stop codon in the last exon of the gene, making it a likely pathogenic variant.

CONCLUSION

Recognition of novel mutations is clinically significant and will contribute to the understanding of the phenotype-genotype relationship of these rare disorders in the future. It also highlights successful fertility outcomes in 11βOHD which have not been well documented in the literature so far.

Clinical, genetic, and structural basis of congenital adrenal hyperplasia due to 11β-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH), resulting from mutations in CYP11B1, a gene encoding 11β-hydroxylase, represents a rare autosomal recessive Mendelian disorder of aberrant sex steroid production. Unlike CAH caused by 21-hydroxylase deficiency, the disease is far more common in the Middle East and North Africa, where consanguinity is common often resulting in identical mutations. Clinically, affected female newborns are profoundly virilized (Prader score of 4/5), and both genders display significantly advanced bone ages and are oftentimes hypertensive. We find that 11-deoxycortisol, not frequently measured, is the most robust biochemical marker for diagnosing 11β-hydroxylase deficiency. Finally, computational modeling of 25 missense mutations of CYP11B1 revealed that specific modifications in the heme-binding (R374W and R448C) or substrate-binding (W116C) site of 11β-hydroxylase, or alterations in its stability (L299P and G267S), may predict severe disease. Thus, we report clinical, genetic, hormonal, and structural effects of CYP11B1 gene mutations in the largest international cohort of 108 patients with steroid 11β-hydroxylase deficiency CAH.

Clinical perspectives in congenital adrenal hyperplasia due to 11β-hydroxylase deficiency

Congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency is a rare autosomal recessive genetic disorder. It is caused by reduced or absent activity of 11β-hydroxylase (CYP11B1) enzyme and the resultant defects in adrenal steroidogenesis. The most common clinical features of 11 beta-hydroxylase deficiency are ambiguous genitalia, accelerated skeletal maturation and resultant short stature, peripheral precocious puberty and hyporeninemic hypokalemic hypertension. The biochemical diagnosis is based on raised serum 11-deoxycortisol and 11-deoxycorticosterone levels together with increased adrenal androgens. More than 100 mutations in CYP11B1 gene have been reported to date. The level of in-vivo activity of CYP11B1 relates to the degree of severity of 11 beta-hydroxylase deficiency. Clinical management of 11 beta-hydroxylase deficiency can pose a challenge to maintain adequate glucocorticoid dosing to suppress adrenal androgen excess while avoiding glucocorticoid-induced side effects. The long-term outcomes of clinical and surgical management are not well studied. This review article aims to collate the current available data about 11 beta-hydroxylase deficiency and its management.