Classic congenital adrenal hyperplasia with unilateral functional adrenal cortical adenoma: case report.

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders related to adrenal steroid biosynthesis, and mainly caused by mutations in the CYP21A2 gene encoding 21-hydroxylase. Adrenal tumors are common in CAH, but functional adrenal tumors are rare. Here, we report a 17-year-old female with virilized external genitalia and primary amenorrhea, accompanied by a right adrenal tumor. Her 17-OHP level was normal, cortisol and androgen levels were significantly elevated, and the tumor pathology showed adrenal cortical adenoma. Gene testing for CYP21A2 showed c.518T > A in exon 4 and c.29313C > G in intron 2. The possibility of untreated classic CAH with 21-OH deficiency causing functional adrenal cortical adenoma should be considered. When clinical diagnosis highly considers CAH and cannot rule out the influence of functional adrenal tumors' secretion function on 17-OHP, gene mutation analysis should be performed.

Rapid detection of common variants and deletions of CYP21A2 using MALDI-TOF MS.

Newborn screening (NBS) for congenital adrenal hyperplasia (CAH) based on hormonal testing is successfully implemented in many countries. However, this method cannot detect non-classic CAH and has high false positive rates. We have developed a novel MALDI-TOF MS assay that can identify common variants and deletions of CYP21A2 in the Chinese population. Thirty-seven clinical patients with CAH confirmed by Sanger sequencing and MLPA analysis were detected by MALDI-TOF MS assay. Two CYP21A2 variants were detected in 30 patients and one CYP21A2 variant was detected in 7 patients. The MALDI-TOF MS assay detected 67 mutant alleles in 37 patients with a detection rate of 90.5%. Sanger sequencing revealed that three variants in seven patients were not included in the designed panel. Eleven distinct CYP21A2 variants were identified, including five missense variants, two nonsense variants, two large gene deletions, one splice variant, and one frameshift variant. The most frequent variant was c.293-13C > G (37.84%), followed by c.518T > A (21.62%) and exon 1-7 deletion (17.57%). The high-throughput MALDI-TOF MS assay that can simultaneously detect common variants and deletions of CYP21A2. This assay can be used for population-based genetic screening and rapid detection of suspected patients, and is expected to be a valuable complement to biochemical-based testing for the detection of CAH.

Congenital Adrenal Hyperplasia with Combined 21-hydroxylase deficiency and 17α-hydroxylase/17,20-lyase deficiency: An undervirilized male.

21-hydroxylase deficiency stands as the most prevalent form of congenital adrenal hyperplasia, primarily resulting from mutations in the CYP21A2 gene. On the other hand, mutations within the CYP17A1 gene lead to 17α-hydroxylase/17,20-lyase enzyme deficiencies. The scarcity of 17-OH deficiency is noteworthy, accounting for less than 1% of all congenital adrenal hyperplasia cases. The male patient, born from a first-degree cousin marriage, exhibited several symptoms, including left undescended testis, micropenis, penile chord, left sensorineural hearing loss, and gynecomastia. He reported micropenis as a concern at the age of 13.5 years. His hormone profile revealed high levels of serum 17-hydroxyprogesterone, progesterone, and pregnenolone. In this case with a 46 XY karyotype, suspicions arose regarding Cytochrome P450 oxidoreductase deficiency due to ambiguous genitalia and an atypical hormone profile. Analysis unveiled two distinct homozygous and pathogenic variants in the CYP21A2 and CYP17A1 genes. Notably, mineralocorticoid precursors escalated, while cortisol and sex steroid precursors decreased during the high (250 mcg) dose ACTH stimulation test. The mutation c.1169C > G (p.Thr390Arg) in CYP17A1, which is the second documented case in literature, stands out due to its unique set of accompanying features. Mutations occurring in CYP21A2 and CYP17A1 result in complete or partial enzyme deficiencies, and the detection of homozygous mutations in two different enzyme systems within the steroidogenic pathway is noteworthy.

Congenital Adrenal Hyperplasia - A Comprehensive Review of Genetic Studies on 21-Hydroxylase Deficiency from India.

Congenital adrenal hyperplasia (CAH) comprises a heterogeneous group of autosomal recessive disorders impairing adrenal steroidogenesis. Most cases are caused by mutations in the CYP21A2 gene resulting in 21-hydroxylase (21-OH) deficiency (21-OHD). The genetics of 21-OH CAH is complexed by a highly homologous pseudogene CYP21A1P imposing several limitations in the molecular analysis. Therefore, genetic testing is still not a part of routine CAH diagnosis and is mainly dependent on 17-hydroxy progesterone (OHP) measurements. There are very few reports of CYP21A2 gene analysis from India and there is no comprehensive review available on genetic testing and the spectrum of CYP21A2 mutations from the country. This review focuses on the molecular aspects of 21-OHD and the genetic studies on CYP21A2 gene reported from India. The results of these studies insist the compelling need for large-scale CYP21A2 genetic testing and newborn screening (NBS) in India. With a high disease prevalence and consanguinity rates, robust and cost-effective genetic testing for 21-OH CAH would enable an accurate diagnosis in routine clinical practice. Whereas establishing affordable genotyping assays even in secondary care or resource-poor settings of the country can identify 90% of the mutations that are pseudogene derived, initiatives on reference laboratories for CAH across the nation with comprehensive genetic testing facilities will be beneficial in those requiring extended analysis of CYP21A2 gene. Further to this, incorporating genetic testing in NBS and carrier screening programmes will enable early diagnosis, better risk assessment and community-based management.

Challenging Molecular Diagnosis of Congenital Adrenal Hyperplasia (CAH) Due to 21-Hydroxylase Deficiency: Case Series and Novel Variants of CYP21A2 Gene.

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive genetic defects in cortisol synthesis and shows elevated ACTH concentrations, which in turn has downstream effects. The most common variant of CAH, 21-hydroxylase deficiency (21OHD), is the result of pathogenic variants in the CYP21A2 gene and is one of the most common monogenic disorders. However, the genetics of 21OHD is complex and challenging. The CYP21A2 gene is located in the RCCX copy number variation (CNV), a complex, multiallelic, and tandem CNV in the major histocompatibility complex (MHC) class III region on chromosome 6 (band 6p21.3). Here, CYP21A2 and its pseudogene CYP21A1P are located 30 kb apart and share a high nucleotide homology of approximately 98% and 96% in exons and introns, respectively. This high-sequence homology facilitates large structural rearrangements, copy number changes, and gene conversion through intergenic recombination. There is a good genotype-phenotype correlation in 21OHD, and genotyping can be performed to confirm the clinical diagnosis, predict long-term outcomes, and determine genetic counseling. Thus, genotyping in CAH is clinically relevant but the interpretations can be challenging for non-initiated clinicians. Here, there are some concrete examples of how molecular diagnosis can sometimes require the use of multiple molecular strategies.

Genetic Disruption of cyp21a2 Leads to Systemic Glucocorticoid Deficiency and Tissues Hyperplasia in the Teleost Fish Medaka (Oryzias latipes).

cytochrome P-450, 21-hydroxylase (cyp21a2), encodes an enzyme required for cortisol biosynthesis, and its mutations are the major genetic cause of congenital adrenal hyperplasia (CAH) in humans. Here, we have generated a null allele for the medaka cyp21a2 with a nine base-pair insertion which led to a truncated protein. We have observed a delay in hatching and a low survival rate in homozygous mutants. The interrenal gland (adrenal counterpart in teleosts) exhibits hyperplasia and the number of pomca-expressing cells in the pituitary increases in the homozygous mutant. A mass spectrometry-based analysis of whole larvae confirmed a lack of cortisol biosynthesis, while its corresponding precursors were significantly increased, indicating a systemic glucocorticoid deficiency in our mutant model. Furthermore, these phenotypes at the larval stage are rescued by cortisol. In addition, females showed complete sterility with accumulated follicles in the ovary while male homozygous mutants were fully fertile in the adult mutants. These results demonstrate that the mutant medaka recapitulates several aspects of cyp21a2-deficiency observed in humans, making it a valuable model for studying steroidogenesis in CAH.

Can incorporating molecular testing improve the accuracy of newborn screening for congenital adrenal hyperplasia?

BACKGROUND: Single-tier newborn screening (NBS) for CAH using 17-hydroxyprogesterone (17OHP) measured by fluoroimmunoassay (FIA) in samples collected at 24-48 hours produces a high false-positive rate (FPR). 2nd tier steroid testing can reduce the FPR and has been widely implemented. We investigated the accuracy of an alternative multi-tier CAH NBS protocol that incorporates molecular testing of the CYP21A2 gene and reduces the 1st tier 17OHP cutoff to minimize missed cases. METHODS: Created a Minnesota-specific CYP21A2 pathogenic variants panel; develop a rapid, high-throughput multiplex, allele-specific-primer-extension assay; perform 1-year retrospective analysis of Minnesota NBS results comparing metrics between a conventional steroid-based two-tier protocol and a molecular-based multi-tier NBS protocol, applied post-hoc. RESULTS: CYP21A2 gene sequencing of 103 Minnesota families resulted in a Minnesota-specific panel of 21 pathogenic variants. Centers for Disease Control and Prevention (CDC) created a molecular assay with 100% accuracy and reproducibility. Two-tier steroid-based screening of 68,659 live births during 2015 resulted in 2 false negatives (FNs), 91 FPs, and 1 true positive (TP). A three-tier protocol with a lower 1st-tier steroid cutoff, 2nd-tier 21-variant CYP21A2 panel and 3rd-tier CYP21A2 sequencing would have resulted in 0 FNs, 52 FPs and 3 TPs. CONCLUSIONS: Incorporation of molecular testing could improve the accuracy of CAH NBS, although some distinct challenges of molecular testing may need to be considered before implementation by NBS programs.

High carrier frequency of CYP21A2 gene mutations in Southern India - underscoring the need for genetic testing in Congenital Adrenal Hyperplasia.

PURPOSE: Congenital Adrenal Hyperplasia (CAH) is one of the highly prevalent autosomal recessive endocrine disorders. The majority of CAH cases result from mutations in the CYP21A2 gene, leading to 21-hydroxylase deficiency. However, with the pseudogene-associated challenges in CYP21A2 gene analysis, routine genetic diagnostics and carrier screening in CAH are not a part of the first-tier investigations in a clinical setting. Furthermore, there is a lack of data on the carrier frequency for 21-OH deficiency. Therefore, this study is aimed at investigating the carrier frequency of common pseudogene derived CYP21A2 mutations in Southern India. METHODS: Recently, a cost-effective Allele-specific PCR based genotyping for CYP21A2 hotspot mutations has been demonstrated to be a highly specific and sensitive assay at the authors' center. Leveraging this approach, a total of 1034 healthy individuals from South India underwent screening to identify the carrier frequency of nine hotspot mutations in the CYP21A2 gene. RESULTS: In this study, it was observed that 9.76% of the subjects were carriers for one or more of the nine different CYP21A2 mutations. Among the carriers, the most common was the large 30 kb deletion, followed by II72N, E6 CLUS, and I2G mutations. CONCLUSION: We have identified a high prevalence of CYP21A2 mutation carriers in Southern India. These findings emphasize the importance of implementing and expanding cost-effective genetic diagnostics and carrier screening throughout India. Such initiatives would play a crucial role in managing the disease burden, enabling early intervention, and establishing guidelines for CAH newborn genetic screening in the country. This study represents the first carrier screening data on CYP21A2 hotspot mutations from India and is the largest study conducted till date in this context.

Rare nonclassic type of Congenital adrenal hyperplasia due to 21-hydroxylase deficiency and genotype-phenotypic correlation.

Objective: To explore the correlation between different CYP21A2 pathogenic gene mutations and clinical phenotypes in Congenital adrenal hyperplasia (CAH) patients. Moreover, combined with the specific phenotypes of patients in the clinic, diagnosis and treatment suggestions should be made for CAH patients. Methods: In this study, a genetic status of a Chinese family in three generations of 21-hydroxylase deficiency was comprehensively presented, and the pathogenic genes in the family were found and traced in detail. We measured CYP21A2 gene in this family by Sanger sequencing and MLPA. The trophoblast cells of female proband's embryos were detected by PGT-M which used Copy-Number Variations of a Single Human Cell and high throughput sequencing. The CYP21A2 gene mutation site in each embryo were detected by Sanger sequencing, whole genome sequencing and single nucleotide polymorphism (SNP). Results: There are many related pathogenic genes of CAH in this family. The female proband showed a compound heterozygous mutation in the CYP21A2 gene, including a CYP21A1P/A2 fusion gene (CH-8) (classical phenotype) and a new mutation c.1034T > C (p. L354S) (unknown clinical significance). In the proband's family, a heterozygous gene mutation of c.1034T > C and a CYP21A1P/A2 fusion gene (CH-8) was carried by her father and mother, respectively. Meanwhile, the husband of the proband also has a genetic family with related disease. Both the husband and his father carried the CYP21A2 gene c.844G > T heterozygous mutation, while his mother had no related mutation in the CYP21A2 gene. Furthermore, PGTM gene detection was carried out on the four blastocysts of the proband's offspring through IVF. The results showed that embryos T1, T2 and T4 all carried CYP21A1P/A2 fusion gene (CH-8), as well as embryo T3 carried c.1034T > C heterozygous mutation of maternal origin. Conclusion: This case is a family report showing a complete genetic map of the proband and her family, describing the genetic process of different pathogenic genes in detail and clearly corresponding to the patient's different phenotypes. It is speculated that the pathogenesis of CAH is caused by different mutations in the CYP21A2 gene and their interactions, which may affect the different phenotypes of CAH patients.

Prenatal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency through molecular genetic analysis of the CYP21A2 gene.

PURPOSE: Deficiency of 21-hydroxylase (21-OHD) is an autosomal recessively inherited disorder that is characterized by adrenal insufficiency and androgen excess. This study was performed to investigate the clinical utility of prenatal diagnosis of 21-OHD using molecular genetic testing in families at risk. METHODS: This study included 27 pregnant women who had previously borne a child with 21-OHD. Fetal tissues were obtained using chorionic villus sampling (CVS) or amniocentesis. After the genomic DNA was isolated, Sanger sequencing of CYP21A2 and multiplex ligation-dependent probe amplification were performed. The clinical and endocrinological findings were reviewed retrospectively. RESULTS: A total of 39 prenatal genetic tests was performed on 27 pregnant women and their fetal tissues. The mean gestational age at the time of testing was 11.7 weeks for CVS and 17.5 weeks for amniocentesis. Eleven fetuses (28.2%) were diagnosed with 21-OHD. Among them, 10 fetuses (90.9%) harbored the same mutation as siblings who were previously diagnosed with 21-OHD. Among these, 4 fetuses (3 males and 1 female) identified as affected were born alive. All 4 patients have been treated with hydrocortisone, 9α-fludrocortisone, and sodium chloride since a mean of 3.7 days of life. The male patients did not show hyponatremia and dehydration, although they harbored pathogenic variants associated with the salt-wasting type of 21-OHD. CONCLUSION: This study demonstrated the diagnostic efficacy and clinical consequences of diagnosis by prenatal genetic testing in families at risk for 21-OHD. All patients identified as affected were treated with hydrocortisone and 9α-fludrocortisone early after birth, which can prevent a life-threatening adrenal crisis.

Evaluating the efficacy of a long-read sequencing-based approach in the clinical diagnosis of neonatal congenital adrenocortical hyperplasia.

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders predominantly characterized by impaired corticosteroid synthesis. Clinical phenotypes include hypoadrenocorticism, electrolyte disturbances, abnormal gonadal development, and short stature, of which severe hyponadrenocorticism and salt wasting can be life-threatening. Genetic analysis can help in the clinical diagnosis of CAH. However, the 21-OHD-causing gene CYP21A2 is arranged in tandem with the highly homologous CYP21A1P pseudogene, making it difficult to determine the exact genotypes using the traditional method of multiplex ligation-dependent probe amplification (MLPA) plus Sanger sequencing or next-generation sequencing (NGS). We applied a long-read sequencing-based approach termed comprehensive analysis of CAH (CACAH) to 48 newborns with CAH that were diagnosed by clinical features and the traditional MLPA plus Sanger sequencing method for retrospective analysis, to evaluate its efficacy in the clinical diagnosis of neonatal CAH. Compared with the MLPA plus Sanger sequencing method, CACAH showed 100 % consistency in detecting SNV/indel variants located in exons and exon-intron boundary regions of CAH-related genes. It can directly determine the cis-trans relationship without the need to analyze parental genotypes, which reduces the time to diagnosis. Moreover, CACAH was able to distinguish different CYP21A1P/CYP21A2 and TNXA/TNXB chimeras, and detect additional variants (CYP21A2 variants c.-121C > T, c.*13G > A, c.*52C > T, c.*440C > T, c.*443 T > C, and TNXB variants c.12463 + 2 T > C, c.12204 + 5G > A). We also identified the TNXB variant c.11435_11524 + 30del alone instead of as a part of the TNXA/TNXB-CH-1 chimera in two newborns, which might be introduced by gene conversion. All of these characteristics enabled clinicians to better explain the phenotype of subjects and manage them more effectively. CACAH has a great advantage over the traditional MLPA and Sanger sequencing methods, showing substantial potential in the genetic diagnosis and screening of neonatal CAH.

Familial ApoB-specific familial hypobetalipoproteinemia in a patient with non-classical congenital adrenal hyperplasia. / Hipobetalipoproteinemia familiar ApoB específica en una paciente con hiperplasia suprarrenal congénita no clásica.

Familial hypobetalipoproteinaemia is a disorder of lipid metabolism characterized by low levels of total cholesterol, low-density lipoprotein cholesterol and apolipoprotein B. ApoB-related familial hypolipoproteinemia is an autosomal condition with a codominance inheritance pattern. Non-classical congenital adrenal hyperplasia is an autosomal recessive disorder due to mutations in the CYP21A2, a gene encoding for the enzyme 21-hydroxylase, which results in an androgen excess production from adrenal source. We here present the case of a 25-year-old woman with NCAH showing decreased levels of total-cholesterol, low-density lipoprotein cholesterol and triglycerides. Her parent had digestive symptoms and severe hepatic steatosis with elevated liver enzymes, as well as decreased levels of total and low-density lipoprotein cholesterol. A genetic-molecular study of the proband identified a mutation in the APOB gene, which allowed a diagnosis of heterozygous ApoB-related hypolipoproteinaemia to be made.

Targeted long-read sequencing for comprehensive detection of CYP21A2 mutations in patients with 21-hydroxylase deficiency.

BACKGROUND: 21-Hydroxylase deficiency (21-OHD) is caused by pathogenic CYP21A2 variations. CYP21A2 is arranged in tandem with its highly homologous pseudogene CYP21A1P; therefore, it is prone to mismatch and rearrangement, producing different types of complex variations. There were few reports on using only one method to detect different CYP21A2 variants simultaneously. AIMS: Targeted long-read sequencing method was used to detect all types of CYP21A2 variants in a series of patients with 21-OHD. METHODS: A total of 59 patients with 21-OHD were enrolled from Peking Union Medical College Hospital. Long-range locus-specific PCR and long-read sequencing (LRS) were performed to detect the pathogenic variants in CYP21A2. RESULTS: Copy-number variants of CYP21A2 were found in 25.4% of patients, including 5.1% with 3 copies of CYP21A2, 16.9% with 1 copy of CYP21A2, and 3.4% with 0 copy of CYP21A2. The remaining 74.6% of patients had 2 copies of CYP21A2. Pathogenic variants were identified in all 121 alleles of 59 patients. Specifically, single-nucleotide variants and small insertions/deletions (< 50 bp) were detected in 79 alleles, of which conversed from CYP21A1P were detected in 63 alleles, and rare variants were found in the other 16 alleles. Large gene conversions (> 50 bp) from pseudogene were detected in 10 alleles, and different chimeric genes (CYP21A1P/CYP21A2 or TNXA/TNXB) formed by large deletions were detected in 32 alleles. Of all variants, p.I173N was the most common variant (19.0%). CONCLUSIONS: Our study demonstrated that targeted long-read sequencing is a comprehensive method for detecting CYP21A2 variations, which is helpful for genetic diagnosis in 21-OHD patients.

Molecular characterization of the new clinical entity associated with congenital adrenal hyperplasia: the CAH-X syndrome in the Spanish population.

Objectives: The chimeras causing the CAH-X syndrome (SCAH-X) result from recombination between CYP21A2-TNXB and their respective pseudogenes (CYP21A1P-TNXA). The clinical manifestations of this syndrome include congenital adrenal hyperplasia (CAH) and Ehlers-Danlos syndrome (EDS). Since SCAH-X has been recently described, the number of publications available is limited. The objective of this study was to set up a molecular approach and a screening algorithm for detecting CAH-X chimeras, determine their frequency and distribution in the Spanish population, and assess their clinical pattern of occurrence in a group of patients. Methods: A total of 186 patients were eligible for CAH-X molecular genetic testing. Testing included MLPA, heterodimer detection by capillary gel electrophoresis, and sequencing of exons 40, 41, and 43 of TNXB. A review was performed of the medical history of 20 patients from three hospitals of reference and the signs and symptoms of EDS they exhibited. Results: In total, 78 CAH patients were carriers of CAH-X chimeras (41.9 %). Forty-six patients were carriers of CH1 (24.7 %), 24 of CH2 (12.9 %), and 8 of CH3 (4.3 %), with a heterogeneous geographical distribution. Seven (35 %) of the 20 carriers of a CAH-X chimera who underwent clinical examination experienced clinical manifestations of EDS. Conclusions: The impact of SCAH-X in the Spanish population was assessed by genetic testing. In the light of the clinical pattern of occurrence and significant prevalence of SCAH-X in the Spanish population, early diagnosis of this entity is essential for an appropriate follow-up of clinical manifestations.

Landscape of Adrenal Tumours in Patients with Congenital Adrenal Hyperplasia.

Our aim is to update the topic of adrenal tumours (ATs) in congenital adrenal hyperplasia (CAH) based on a multidisciplinary, clinical perspective via an endocrine approach. This narrative review is based on a PubMed search of full-length, English articles between January 2014 and July 2023. We included 52 original papers: 9 studies, 8 case series, and 35 single case reports. Firstly, we introduce a case-based analysis of 59 CAH-ATs cases with four types of enzymatic defects (CYP21A2, CYP17A1, CYP17B1, and HSD3B2). Secondarily, we analysed prevalence studies; their sample size varied from 53 to 26,000 individuals. AT prevalence among CAH was of 13.3-20%. CAH prevalence among individuals with previous imaging diagnosis of AT was of 0.3-3.6%. Overall, this 10-year, sample-based analysis represents one of the most complex studies in the area of CAH-ATs so far. These masses should be taken into consideration. They may reach impressive sizes of up to 30-40 cm, with compressive effects. Adrenalectomy was chosen based on an individual multidisciplinary decision. Many tumours are detected in subjects with a poor disease control, or they represent the first step toward CAH identification. We noted a left lateralization with a less clear pathogenic explanation. The most frequent tumour remains myelolipoma. The risk of adrenocortical carcinoma should not be overlooked. Noting the increasing prevalence of adrenal incidentalomas, CAH testing might be indicated to identify non-classical forms of CAH.

Generation of human steroidogenic cytochrome P450 enzymes for structural and functional characterization.

Six cytochrome P450 enzymes are involved in human steroidogenesis, converting cholesterol to sex steroids, mineralocorticoids, and glucocorticoids. While early work was accomplished with steroidogenic P450 orthologs from more accessible sources, knowledge of basic biochemistry through successful drug design have been greatly facilitated by recombinantly-expressed, highly purified human versions of these membrane proteins. Many membrane proteins are difficult to express and purify and are unstable. Membrane P450 expression in E. coli has been facilitated by modification and/or truncation of the membrane-interacting N-terminus, while metal-affinity resins and histidine-tagging greatly facilitates purification. However, substantial optimization is still frequently required to maintain protein stability. Over time, a generalized three-column purification scheme has been developed and tweaked to generate substantial quantities of fully active, highly purified human cytochrome P450 enzymes that have made possible the application of many structural, biochemical, and biophysical techniques to elucidate the mysteries of these critical human enzymes.

Molecular basis and genetic testing strategies for diagnosing 21-hydroxylase deficiency, including CAH-X syndrome.

Congenital adrenal hyperplasia (CAH) is a group of autosomally recessive disorders that result from impaired synthesis of glucocorticoid and mineralocorticoid. Most cases (~95%) are caused by mutations in the CYP21A2 gene, which encodes steroid 21-hydroxylase. CAH patients manifest a wide phenotypic spectrum according to their degree of residual enzyme activity. CYP21A2 and its pseudogene (CYP21A1P) are located 30 kb apart in the 6q21.3 region and share approximately 98% of their sequences in the coding region. Both genes are aligned in tandem with the C4, SKT19, and TNX genes, forming 2 segments of the RCCX modules that are arranged as STK19-C4A-CYP21A1P-TNXA-STK19B-C4B-CYP21A2-TNXB. The high sequence homology between the active gene and pseudogene leads to frequent microconversions and large rearrangements through intergenic recombination. The TNXB gene encodes an extracellular matrix glycoprotein, tenascin-X (TNX), and defects in TNXB cause Ehlers-Danlos syndrome. Deletions affecting both CYP21A2 and TNXB result in a contiguous gene deletion syndrome known as CAH-X syndrome. Because of the high homology between CYP21A2 and CYP21A1P, genetic testing for CAH should include an evaluation of copy number variations, as well as Sanger sequencing. Although it poses challenges for genetic testing, a large number of mutations and their associated phenotypes have been identified, which has helped to establish genotype-phenotype correlations. The genotype is helpful for guiding early treatment, predicting the clinical phenotype and prognosis, and providing genetic counseling. In particular, it can help ensure proper management of the potential complications of CAH-X syndrome, such as musculoskeletal and cardiac defects. This review focuses on the molecular pathophysiology and genetic diagnosis of 21-hydroxylase deficiency and highlights genetic testing strategies for CAH-X syndrome.

The pathogenic p.Gln319Ter variant is not causing congenital adrenal hyperplasia when inherited in one of the duplicated CYP21A2 genes.

Objective: The study aimed to identify the pathogenic status of p.Gln319Ter (NM_000500.7: c.955C>T) variant when inherited in a single CYP21A2 gene (bimodular RCCX haplotype) and to discriminate between a non-causing congenital adrenal hyperplasia (CAH) allele when inherited in a duplicated and functional CYP21A2 gene context (trimodular RCCX haplotype). Methods: 38 females and 8 males with hyperandrogenemia, previously screened by sequencing and identified as carriers for the pathogenic p.Gln319Ter, were herein tested by multiplex ligation-dependent probe amplification (MLPA) and a real-time PCR Copy number Variation (CNV) assay. Results: Both MLPA and real-time PCR CNV analyses confirmed a bimodular and pathogenic RCCX haplotype with a single CYP21A2 in 19/46 (41.30%) p.Gln319Ter carriers and who in parallel all shared elevated 17-OHP levels. The remaining 27 individuals that also carried the p.Gln319Ter exhibited low 17-OHP levels as a result of their carriership of a duplicated CYP21A2 with a trimodular RCCX haplotype. Interestingly, all of these individuals also carried in linkage disequilibrium with p.Gln319Ter two single nucleotide polymorphisms, the c.293-79G>A (rs114414746) in intron 2 and the c.*12C>T (rs150697472) in the 3'-UTR. Therefore, these variants can be used to distinguish between pathogenic and non-pathogenic genomic contexts of the c.955T (p.Gln319) in the genetic diagnosis of congenital adrenal hyperplasia (CAH). Conclusion: The employed methodologies identified a considerable number of individuals with non-pathogenic p.Gln319Ter from the individuals that typically carry the pathogenic p.Gln319Ter in a single CYP21A2. Therefore, it is extremely important the detection of such haplotypes for the prenatal diagnosis, treatment and genetic counseling in patients with CAH.

The prevalence and genotype of 21-hydroxylase deficiency in the Croatian Romani population.

Objective: Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency (21-OHD) is a rare autosomal recessive disorder caused by pathological variants in the CYP21A2 gene. After a high prevalence of classic 21-OHD CAH in the Romani population was reported in the Republic of North Macedonia, we decided to estimate the prevalence of 21-OHD in Croatia and, if high, assess the possible causes and estimate the frequency of particular CYP21A2 variants. Design: Cross-sectional study. Methods: Data from a Croatian 21-OHD genetic database was reviewed, and only Romani patients were included in the study. CYP21A2 genotyping was performed using allele-specific PCR, MLPA, and Sanger sequencing. Results: According to a survey conducted in 2017, Croatia had 22,500 Romani people and six of them had a salt-wasting (SW) form of 21-OHD. All were homozygous for the c.IVS2-13A/C-G pathological variant in intron 2 and descended from consanguineous families belonging to different Romani tribes. The calculated prevalence of 21-OHD in Croatian Romani is 1:3,750, while in the Croatian general population, it is 1:18,000. Three of the six Romani patients originated from two neighboring villages in North-western Croatia (Slavonia County), as well as the seventh patient who is of mixed Romani/Croatian descent and heterozygous for the c.IVS2-13A/C-G pathological variant (not included in the prevalence calculation). Conclusion: A high prevalence of SW 21-OHD in the Croatian Romani population caused by the homozygous cIVS2-13A/C-G pathological variant was found. In addition to isolation and consanguinity, other possible reasons could be the heterozygous advantage of the CYP21A2 gene pathological variant and the bottleneck effect as a result of the Romani Holocaust in World War II.

Long-read sequencing: An effective method for genetic analysis of CYP21A2 variation in congenital adrenal hyperplasia.

BACKGROUND: The sequence similarity between CYP21A2 gene and its inactive pseudogene CYP21A1P, and copy number variation (CNV) caused by unequal crossover, make it challenging to characterize the CYP21A2 gene through traditional methods. This study aimed to evaluate the clinical utility of the long-read sequencing (LRS) method in carrier screening and genetic diagnosis of congenital adrenal hyperplasia (CAH) by comparing the efficiency of the LRS method with the conventional multiplex ligation-dependent probe amplification (MLPA) plus Sanger sequencing approaches in CYP21A2 analysis. METHODS: In a retrospective study, full sequence analysis of the CYP21A2 and CYP21A1P was performed for three pedigrees through long-range locus-specific PCR followed by LRS based on the Pacific Biosciences (PacBio, California, USA) single-molecule real-time (SMRT) platform, and the results were compared with those obtained from next-generation sequencing (NGS)-based whole exome sequencing (WES) and the traditional methods of MLPA plus Sanger sequencing. RESULTS: The LRS method successfully identified seven CYP21A2 variants, including three single nucleotide variants (NM_000500.9:c.1451G > C p.(Arg484Pro), c.293-13A/C > G (IVS2-13A/C > G), c.518 T > A p.(Ile173Asn)), one 111-bp polynucleotide insertion, one set of 3'URT variants (NM_000500.9:c.*368 T > C, c.*390A > G, c.*440C > T, c.*443 T > C) and two types of chimeric genes and straightforwardly depicted the inheritance patterns of these variants within families. Moreover, the LRS method enabled us to determine the cis-trans configuration of multiple variants in one assay, without the need to analyze additional family samples. Compared with traditional methods, this LRS method can achieve a precise, comprehensive and intuitive result in the genetic diagnosis of 21-hydroxylase deficiency (21-OHD). CONCLUSION: The LRS method is comprehensive in CYP21A2 analysis and intuitive in result presentation, which holds substantial promise in clinical application as a crucial tool for carrier screening and genetic diagnosis of CAH.