GENETICS IN ENDOCRINOLOGY: Approaches to molecular genetic diagnosis in the management of differences/disorders of sex development (DSD): position paper of EU COST Action BM 1303 ‘DSDnet’

The differential diagnosis of differences or disorders of sex development (DSD) belongs to the most complex fields in medicine. It requires a multidisciplinary team conducting a synoptic and complementary approach consisting of thorough clinical, hormonal and genetic workups. This position paper of EU COST (European Cooperation in Science and Technology) Action BM1303 ‘DSDnet’ was written by leading experts in the field and focuses on current best practice in genetic diagnosis in DSD patients. Ascertainment of the karyotpye defines one of the three major diagnostic DSD subclasses and is therefore the mandatory initial step. Subsequently, further analyses comprise molecular studies of monogenic DSD causes or analysis of copy number variations (CNV) or both. Panels of candidate genes provide rapid and reliable results. Whole exome and genome sequencing (WES and WGS) represent valuable methodological developments that are currently in the transition from basic science to clinical routine service in the field of DSD. However, in addition to covering known DSD candidate genes, WES and WGS help to identify novel genetic causes for DSD. Diagnostic interpretation must be performed with utmost caution and needs careful scientific validation in each DSD case.

Expression and activity profiling of the steroidogenic enzymes of glucocorticoid biosynthesis and the fdx1 co-factors in zebrafish

The spatial and temporal expression of steroidogenic genes in zebrafish has not been fully characterised. Because zebrafish are increasingly employed in endocrine and stress research, a better characterisation of steroidogenic pathways is required to target specific steps in the biosynthetic pathways. In the present study, we have systematically defined the temporal and spatial expression of steroidogenic enzymes involved in glucocorticoid biosynthesis (cyp21a2, cyp11c1, cyp11a1, cyp11a2, cyp17a1, cyp17a2, hsd3b1, hsd3b2), as well as the mitochondrial electron-providing ferredoxin co-factors (fdx1, fdx1b), during zebrafish development. Our studies showed an early expression of all these genes during embryogenesis. In larvae, expression of cyp11a2, cyp11c1, cyp17a2, cyp21a2, hsd3b1 and fdx1b can be detected in the interrenal gland, which is the zebrafish counterpart of the mammalian adrenal gland, whereas the fdx1 transcript is mainly found in the digestive system. Gene expression studies using quantitative reverse transcriptase-PCR and whole-mount in situ hybridisation in the adult zebrafish brain revealed a wide expression of these genes throughout the encephalon, including neurogenic regions. Using ultra-high-performance liquid chromatography tandem mass spectrometry, we were able to demonstrate the presence of the glucocorticoid cortisol in the adult zebrafish brain. Moreover, we demonstrate de novo biosynthesis of cortisol and the neurosteroid tetrahydrodeoxycorticosterone in the adult zebrafish brain from radiolabelled pregnenolone. Taken together, the present study comprises a comprehensive characterisation of the steroidogenic genes and the fdx co-factors facilitating glucocorticoid biosynthesis in zebrafish. Furthermore, we provide additional evidence of de novo neurosteroid biosynthesising in the brain of adult zebrafish facilitated by enzymes involved in glucocorticoid biosynthesis. Our study provides a valuable source for establishing the zebrafish as a translational model with respect to understanding the roles of the genes for glucocorticoid biosynthesis and fdx co-factors during embryonic development and stress, as well as in brain homeostasis and function.

Steroid hormone analysis in diagnosis and treatment of DSD: position paper of EU COST Action BM 1303 'DSDnet'

Disorders or differences in sex development (DSD) comprise a heterogeneous group of conditions with an atypical sex development. For optimal diagnosis, highly specialised laboratory analyses are required across European countries. Working group 3 of EU COST (European Cooperation in Science and Technology) Action BM 1303 'DSDnet' 'Harmonisation of Laboratory Assessment' has developed recommendations on laboratory assessment for DSD regarding the use of technologies and analytes to be investigated. This position paper on steroid hormone analysis in diagnosis and treatment of DSD was compiled by a group of specialists in DSD and/or hormonal analysis, either from participating European countries or international partner countries. The topics discussed comprised analytical methods (immunoassay/mass spectrometry-based methods), matrices (urine/serum/saliva) and harmonisation of laboratory tests. The following positions were agreed upon: support of the appropriate use of immunoassay- and mass spectrometry-based methods for diagnosis and monitoring of DSD. Serum/plasma and urine are established matrices for analysis. Laboratories performing analyses for DSD need to operate within a quality framework and actively engage in harmonisation processes so that results and their interpretation are the same irrespective of the laboratory they are performed in. Participation in activities of peer comparison such as sample exchange or when available subscribing to a relevant external quality assurance program should be achieved. The ultimate aim of the guidelines is the implementation of clinical standards for diagnosis and appropriate treatment of DSD to achieve the best outcome for patients, no matter where patients are investigated or managed.

Adrenal Steroid Metabolites Accumulating in Congenital Adrenal Hyperplasia Lead to Transactivation of the Glucocorticoid Receptor

Patients with congenital adrenal hyperplasia (CAH) are often clinically less severely affected by cortisol deficiency than anticipated from their enzymatic defect. We hypothesize that adrenal steroid hormone precursors that accumulate in untreated or poorly controlled CAH have glucocorticoid activity and partially compensate for cortisol deficiency. We studied the in vitro effects of 17-hydroxyprogesterone (17OHP), progesterone (P), 21-deoxycortisol (21DF), and androstenedione (Δ4) on the human glucocorticoid receptor (hGR). Competitive binding assays were performed in HeLa cells. Nuclear translocation of the hGR was studied by transfection of COS-7 cells with a GFP-tagged hGR and fluorescence microscopy. Transactivation assays were performed in COS-7 cells and in HEK 293 cells after cotransfection with hGR and luciferase reporter vectors using a dual luciferase assay. 17OHP, P, and 21DF are able to bind to the hGR with binding affinities of 24-43% compared with cortisol. Δ4 has a low binding affinity. Incubation with 21DF led to complete nuclear translocation of the hGR, whereas treatment with 17OHP or P resulted in partial nuclear translocation. 21DF transactivated the hGR with an EC50 approximately 6 times the EC50 of cortisol. 17OHP and P transactivated the hGR with EC50s of more than 100 times the EC50 of cortisol. No hGR transactivation was detected after incubation with Δ4. 21DF, 17OHP, and P are able to bind, translocate, and transactivate the hGR in vitro and thus may have glucocorticoid activity. 21DF might have a clinically relevant agonistic effect on the hGR and could potentially partially compensate the cortisol deficiency in CAH patients.

Relationship between final height and health outcomes in adults with congenital adrenal hyperplasia: United Kingdom congenital adrenal hyperplasia adult study executive (CaHASE)

CONTEXT

Treatment of congenital adrenal hyperplasia (CAH) in childhood focuses on growth and development and adult final height (FH) is a measure of effective treatment. We hypothesized that shorter adults will have more severe underlying disease and worse health outcomes.

METHODS

This was a cross-sectional analysis of 199 adults with CAH. FH and quality of life were expressed as z-scores adjusted for midparental target height or UK population height.

RESULTS

FH correlated inversely with age (men, r = -0.38; women, r = -0.26, P < .01). Men and women had z-scores adjusted for midparental target height of -2 and -1, respectively, and both groups had UK population height z-scores of -1 below the UK population (P < .01). In women, FH was shorter in non-salt-wasting than salt-wasting classic CAH (P < .05) and in moderately affected genotype group B women than either more severely affected groups null and A (P < .01) or the mildest group C (P < .001). Short stature and a higher prevalence of hypertension were observed in classic CAH patients diagnosed late (after 1 y) compared with those diagnosed early and in women treated with glucocorticoid only compared with those treated with both glucocorticoids and mineralocorticoids (P < .05). FH did not associate with insulin sensitivity, lipid profile, adiposity, or quality of life.

CONCLUSIONS

Adult CAH patients remain short, although height prognosis has improved over time. The shortest adults are those diagnosed late with moderate severity CAH and are at increased risk of adult hypertension; we hypothesize that these patients are exposed in childhood to high androgens and/or excessive glucocorticoids with potential programming of hypertension. Another possibility is inadequate mineralocorticoid treatment early in life in the late-diagnosed patient group. Prospective studies are now required to examine these hypotheses.

Glucocorticoid treatment regimen and health outcomes in adults with congenital adrenal hyperplasia

BACKGROUND

Adults with congenital adrenal hyperplasia (CAH) are treated with a wide variety of glucocorticoid treatment regimens.

OBJECTIVE, DESIGN AND METHODS

To test whether drug dose and timing of glucocorticoid treatment regimen impacts on health outcomes. This was a cross-sectional study of 196 adult CAH patients in whom treatment and health outcomes were measured. Glucocorticoid dose was converted to prednisolone dose equivalent (PreDEq) using three published formulae. Associations between the type of glucocorticoid regimen and PreDEq with specific health outcome variables were tested using partial correlation and principal components analysis (PCA).

RESULTS

Patients on dexamethasone had lower androgens and ACTH but greater insulin resistance compared with those receiving hydrocortisone or prednisolone. Dexamethasone dose and once daily administration were associated with insulin resistance. Partial correlation analysis adjusted for age and sex showed PreDEq weakly correlated (r < 0·2) with blood pressure and androstenedione. Mutation severity was associated with increased PreDEq (F(3,141)  = 4·4, P < 0·01). In PCA, 3 PCs were identified that explained 62% of the total variance (r(2) ) in observed variables. Regression analysis (age and sex adjusted) confirmed that PC2, reflecting disease control (androstenedione, 17-hydroxypregesterone and testosterone), and PC3, reflecting blood pressure and mutations (systolic and diastolic blood pressure and mutation severity), related directly to PreDEq (r(2)  = 23%, P < 0·001).

CONCLUSIONS

In adults with congenital adrenal hyperplasia, dexamethasone use was associated with lower androgens but greater insulin resistance, and increasing glucocorticoid dose associated with increased blood pressure, poor disease control and mutation severity.

Novel H6PDH mutations in two girls with premature adrenarche: 'apparent' and 'true' CRD can be differentiated by urinary steroid profiling

CONTEXT

Inactivating mutations in the enzyme hexose-6-phosphate dehydrogenase (H6PDH, encoded by H6PD) cause apparent cortisone reductase deficiency (ACRD). H6PDH generates cofactor NADPH for 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1, encoded by HSD11B1) oxo-reductase activity, converting cortisone to cortisol. Inactivating mutations in HSD11B1 cause true cortisone reductase deficiency (CRD). Both ACRD and CRD present with hypothalamic-pituitary-adrenal (HPA) axis activation and adrenal hyperandrogenism.

OBJECTIVE

To describe the clinical, biochemical and molecular characteristics of two additional female children with ACRD and to illustrate the diagnostic value of urinary steroid profiling in identifying and differentiating a total of six ACRD and four CRD cases.

DESIGN

Clinical, biochemical and genetic assessment of two female patients presenting during childhood. In addition, results of urinary steroid profiling in a total of ten ACRD/CRD patients were compared to identify distinguishing characteristics.

RESULTS

Case 1 was compound heterozygous for R109AfsX3 and a novel P146L missense mutation in H6PD. Case 2 was compound heterozygous for novel nonsense mutations Q325X and Y446X in H6PD. Mutant expression studies confirmed loss of H6PDH activity in both cases. Urinary steroid metabolite profiling by gas chromatography/mass spectrometry suggested ACRD in both cases. In addition, we were able to establish a steroid metabolite signature differentiating ACRD and CRD, providing a basis for genetic diagnosis and future individualised management.

CONCLUSIONS

Steroid profile analysis of a 24-h urine collection provides a diagnostic method for discriminating between ACRD and CRD. This will provide a useful tool in stratifying unresolved adrenal hyperandrogenism in children with premature adrenarche and adult females with polycystic ovary syndrome (PCOS).

No correlation between androgen receptor CAG and GGN repeat length and the degree of genital virilization in females with 21-hydroxylase deficiency

CONTEXT

In 21-hydroxylase (CYP21A2) deficiency (21OHD), the level of in vitro enzymatic function allows for classification of mutation groups (null, A, B, C) and prediction of disease severity. However, genital virilization in affected females correlates only weakly with CYP21A2 mutation groups, suggesting the influence of genetic modifiers.

OBJECTIVE

The objective of the study was to investigate the influence of the polymorphic CAG and GGn repeats of the androgen receptor (AR) gene on the degree of genital virilization in 21OHD females.

DESIGN AND PATIENTS

Design of the study was the determination of CYP21A2 genotype, degree of genital virilization (Prader stage), and X-weighted biallelic mean of AR CAG and GGn repeat length in 205 females with 21OHD.

OUTCOME MEASUREMENTS

Correlation of AR CAG and GGn repeat lengths with Prader stages using nested stepwise logistic regression analysis was measured.

RESULTS

CYP21A2 mutation groups null and A showed significantly higher levels of genital virilization than groups B and C (P < 0.01). However, Prader stages varied considerably within mutation groups: null, Prader I-V (median IV); A, Prader I-V (median IV); B, Prader I-V (median III); C, 0-III (median I). Mean GGn repeat length of patients was not significantly associated with Prader stages, classified as low (0-I), intermediate (II-III), or severe (IV-V) (odds ratio per repeat: 0.98, 95% confidence interval 0.71-1.35). In contrast, patients with Prader 0-I showed a trend toward longer CAG repeats without reaching statistical significance (P = 0.07, odds ratio per repeat: 0.82, 95% confidence interval 0.65-1.02).

CONCLUSION

Neither CAG nor GGn repeat lengths are statistically significant modifiers of genital virilization in females with 21OHD.

Extreme hyponatremia in an infant with congenital adrenal hypoplasia due to a novel NR0B1 (DAX-1) mutation

BACKGROUND

Extreme hyponatremia (<105 mmol/l) has rarely been reported in infants. It is potentially life-threatening and requires intensive care treatment.

PATIENT

We report on a male infant with absence of weight gain from birth to day 33 of life despite adequate nutrition. On admission serum sodium and potassium were 104 and 5.9 mmol/L respectively. The infant's physical status revealed dehydration, but normal activity with no apparent neurological, circulatory or respiratory impairment.

MAIN RESULTS

Global adrenocortical insufficiency was diagnosed and treated with hormonal substitution in addition to intravenous application of fluid, glucose and electrolytes. The rise of serum sodium was carefully monitored and adjusted to a target rate of 0.5 mmol/L/h. X-linked adrenal hypoplasia congenita (X-AHC) was confirmed by the identification of a novel nonsense NR0B1 (DAX-1) mutation (W236X).

CONCLUSIONS

X-AHC in infants may present as failure to thrive despite adequate nutrition. Extreme hyponatremia may be associated with little symptoms if developing slowly. Rehydration and slow correction of serum sodium with solutions containing less sodium than normal saline is essential.

Initially elevated TSH and congenital central hypothyroidism due to a homozygous mutation of the TSH beta subunit gene: case report and review of the literature

Congenital central hypothyroidism (CCH) is a rare disease which can be caused by mutations in the gene for the thyrotropin (TSH) beta subunit ( TSHB). The diagnosis is usually delayed because the TSH serum levels in these patients are not elevated leading to a negative result in the neonatal TSH screening. Herein, we report a 2-year-old girl with CCH due to a mutation in the TSHB gene, in whom the unusual finding of an initially elevated TSH level complicated the diagnostic workup. The proposita, who had a supposedly normal TSH screening result, is a German girl of non-consanguineous parents. At 5 weeks of age, her thyroid function tests showed peripheral hypothyroidism with a moderately increased TSH (23.8 microIU/ml) so that thyroid hormone substitution was initiated. At the age of 2 years, the administration of TRH failed to increase the TSH serum concentrations, which prompted TSH measurements with two different assay systems. Variable TSH levels ranging from not detectable low to elevated were found so that central hypothyroidism due to a mutation in the TSHB gene was suspected. This was confirmed by molecular analysis of the TSHB gene, which identified a homozygous deletion (delta 313 T) in the coding sequence. This mutation has been found in the German population before and may be a founder mutation. We conclude that depending on the assay system variable TSH serum levels in individuals with mutations in the TSHB gene may complicate the diagnostic workup.

Absence of exercise-induced leptin suppression associated with insufficient epinephrine reserve in patients with classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency

OBJECTIVE

Patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency suffer from glucocorticoid and mineralocorticoid deficiency. They have insufficient epinephrine reserves and increased basal leptin levels and are often insulin resistant. In healthy subjects, an inhibitory effect of acute catecholamine elevation on the leptin plasma concentrations has been reported. However, it is not yet known how leptin levels respond to exercise in CAH patients.

METHODS

We performed a cycle ergometer test in six CAH patients to measure the response of plasma leptin, glucose and the catecholamines, epinephrine (E) and norepinephrine (N), as well as their respective metabolites, metanephrine (M) and normetanephrine (NM), to intense exercise.

RESULTS

Baseline leptin concentrations in CAH patients were not different from those of controls. Leptin levels decreased significantly with exercise in healthy controls, whereas they remained unchanged in CAH patients. In contrast to controls, CAH patients showed no rise of plasma glucose. Basal and stimulated E and M levels were significantly lower in CAH patients compared to controls. Baseline and stimulated N and NM levels were comparable, showing a significant rise after exercise. Peak systolic blood pressure and peak heart rate in both groups were comparable.

CONCLUSION

CAH patients do not manifest exercise-induced leptin suppression. The most probable reason for this is their severely impaired epinephrine stress response. In addition, epinephrine deficiency is leading to secondary changes in various catecholamine dependent metabolic pathways, e. g., energy balance. Although obvious clinical sequelae are so far unknown, the catecholamine-deficient state and the resulting hyperleptinemia might contribute to the severity of the disease in CAH.

Three novel point mutations of the CYP21 gene detected in classical forms of congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) [OMIM 201 910] is a group of autosomal recessive disorders most commonly due to 21-hydroxylase deficiency and presenting with a wide range of clinical manifestations. A limited number of inactivating pseudogene-derived mutations account for the majority of 21-hydroxylase gene ( CYP21) mutations, additional rare mutations can be found in single families and small populations. We found three novel CYP21 mutations in CAH patients suffering from the classical form of the disease, of which one is a frameshift mutation (1353-1354insA) leading to a premature termination codon (K277K, Q228A...E294X), one results in a premature stop codon (2551C>T, R444X), and one is a missense mutation (2609T>C; P463L). The frameshift and premature stop mutations can be predicted to result in a CYP21 protein without any residual enzyme activity. To determine the functional consequences of the P463L mutation, the IN VITRO enzyme activity was studied in COS-7 cells and revealed a reduced 21-hydroxylase activity of 2.6+/-0.8 (SD)% for the conversion of 17-hydroxyprogesterone (17OHP) to 11-deoxycortisol and of 3.0+/-0.5 % for the conversion of progesterone to 11-deoxycorticosterone (DOC). We conclude that functional analyses of unknown mutations provide information on the disease severity and should be always performed when novel CYP21 mutations are detected. Knowledge of the residual 21-hydroxylase function improves both genetic counselling and individual clinical management in CAH patients.

Congenital adrenal hyperplasia - how to improve the transition from adolescence to adult life

Congenital adrenal hyperplasia (CAH) is caused by a defect in the biosynthesis of cortisol that results in maximal activity of the hypothalamic-pituitary adrenal axis with hyperplasia of the adrenals and hyperandrogenism due to the accumulation of androgen precursors. In the salt-wasting subtype of the disorder, which accounts for appr. 75 % of patients with classical CAH, patients are unable to synthesise sufficient amounts of aldosterone and are prone to life-threatening salt-losing crises, whereas the simple virilising form is predominantly characterized by clitoris hypertrophy and posterior labial fusion. In addition, a non-classical variant can be discerned which in most cases is diagnosed at the time of puberty or early adolescence when hirsutism and menstrual irregularities may occur. The vast majority of CAH patients have 21-hydroxylase deficiency (90 - 95 %). Less common forms, such as 11beta-hydroxylase deficiency, will not be discussed in this review. Unfortunately, a considerable number of CAH patients is lost to regular and competent follow-up once they move out of paediatric care. This is most probably the result of insufficient co-operation between paediatric and adult endocrinologists at the time of transition from adolescence to adulthood. Furthermore, there is a lack of clinical guidance regarding psychosexual development in these patients. In this overview we will focus on special aspects of CAH treatment in adolescence and adulthood, and report on our 10-year experience with a transfer system for endocrine patients from paediatric to internal medical care, known as the "Kieler Modell". For practical purposes, we here provide charts for follow-up of CAH patients that can be adapted for use in any endocrine outpatient clinic.

Chromatographic system for the simultaneous measurement of plasma 18-hydroxy-11-deoxycorticosterone and 18-hydroxycorticosterone by radioimmunoassay: reference data for neonates and infants and its application in aldosterone-synthase deficiency

A new chromatographic system for the steroid precursor separation and a sensitive radioimmunoassay system for the subsequent measurement of 18-hydroxy-11-deoxycorticosterone and 18-hydroxycorticosterone has been developed. 18-Hydroxy-11-deoxycorticosterone and 18-hydroxycorticosterone were extracted with methylene chloride and separated from cross-reacting steroids by Sephadex LH-20 column chromatography. Anti-18-hydroxy-11-deoxycorticosterone and anti-18-hydroxycorticosterone antibodies raised in rabbits were used. The lower detection limit of the assay is 0.03 nmol/l and 0.128 nmol/l for 18-hydroxy-11-deoxycorticosterone and 18-hydroxycorticosterone, respectively. Normal values for this assay in 128 healthy neonates and infants aged 0-5 months were established as a basis for the early hormonal diagnosis of aldosterone synthase deficiency types I and II. Its application for the diagnosis of aldosterone synthase deficiency is demonstrated in two patients with homozygous mutation/deletion in the encoding CYP11B2 gene.

CYP21 mutations in simple virilizing congenital adrenal hyperplasia

We studied the functional and structural effects of two unique missense mutations in CYP21 found in patients with simple virilizing congenital adrenal hyperplasia. The rare variants L300F and V281G were found in two girls who were each hemizygous for one of the mutations. Functional analysis after expression in COS-1 cells revealed that the mutant enzymes had reduced enzymatic activity for conversion of both 17-hydroxyprogesterone (L300F 9.5%, V281G 3.9% of normal) and progesterone (L300F 4.4%, V281G 3.9% of normal). Both mutant enzymes had an increased degradation in mammalian COS-1 cells compared to the normal protein, although the L300F variant affected the degradation pattern to a greater extent. Our data indicate that the residue L300 is important in maintaining normal structure of the 21-hydroxylase enzyme whereas mutations affecting V281 most likely cause impaired enzyme activity by interfering with a specific function(s) of the protein.

Mothers with congenital adrenal hyperplasia and their children: outcome of pregnancy, birth and childhood

OBJECTIVES

Fertility rates in women with congenital adrenal hyperplasia (CAH) are reported to be poor, but few data are available. We assessed rates and course of pregnancy, mode of delivery and long-term outcome of offspring from women with CAH.

DESIGN

A large cohort of women with CAH due to 21-hydroxylase deficiency had initially been diagnosed and followed at one centre. Those women who had given birth were contacted. Information was gathered from hospital records, direct patient contact, structured questionnaire and the Documentation of Pregnancy and Preventive Care Booklets.

RESULTS

Between 1978 and 1998, 18 women with CAH (one salt wasting, 12 simple virilizing, five nonclassical) had given birth to 31 children (18 females, 13 males). Delivery was by Caesarean section in 16 out of the 31 children. None of the female newborns was masculinized. Twenty-nine children were born at term, five children were small for gestational age (SGA). Postnatal development was basically normal in all children; 18 are now older than 10 years, seven are between 5 and 10 years old, six are less than 5 years old.

CONCLUSIONS

Fertility is reduced in females with CAH, especially those with the severe or salt wasting phenotype. In those women with CAH who do conceive, course and outcome of pregnancy is mostly uneventful, although the rate of SGA offspring may be increased. Psychomotor and somatic long-term development of the children was within normal limits.

A novel frameshift mutation (141delT) in exon 1 of the 21-hydroxylase gene (CYP21) in a patient with the salt wasting form of congenital adrenal hyperplasia. Mutation in brief no. 255. Online

Congenital adrenal hyperplasia (CAH) is a common autosomal recessive disease with a wide range of clinical manifestation. In 90-95% of the cases it is caused by 21-hydroxylase deficiency (OMIM #201910) due to mutations of the CYP21 gene (GDB Accession #M12792). In most cases the CYP21-inactivating point mutations are transferred by apparent gene conversions from CYP21P to CYP21. In only a few cases point mutations have been described, which are not present in the pseudogene. Using Southern blot analysis and DNA sequencing we have identified a novel mutation (141delT) of the CYP21 gene in a patient suffering from the salt wasting form of CAH. This results in a premature termination of a truncated protein at amino acid position 51 (L51X), which is likely to result in an enzyme with no activity. This novel mutation has not been reported to occur in the CYP21P alleles and it was not found in the CYP21P alleles in this CAH family.

Predicting phenotype in steroid 21-hydroxylase deficiency? Comprehensive genotyping in 155 unrelated, well defined patients from southern Germany

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders. CAH is most often caused by deficiency of steroid 21-hydroxylase. The frequency of CYP21-inactivating mutations and the genotype-phenotype relationship were characterized in 155 well defined unrelated CAH patients. We were able to elucidate 306 of 310 disease-causing alleles (diagnostic sensitivity, 98.7%). The most frequent mutation was the intron 2 splice site mutation (30.3%), followed by gene deletions (20.3%), the I172N mutation (19.7%) and large gene conversions (7.1%). Five point mutations were detected that have not been described in other CAH cohorts. Genotypes were categorized in 4 mutation groups (null, A, B, and C) according to their predicted functional consequences and compared to the clinical phenotype. The positive predictive value for null mutations (ppv(null)) was 100%, as all patients with these mutations had a salt-wasting phenotype. In mutation group A (intron 2 splice site mutation in homozygous or heterozygous form with a null mutation), the ppv(A) to manifest with salt-wasting CAH was 90%. In group B predicted to result in simple virilizing CAH (I172N in homozygous or compound heterozygous form with a more severe mutation), ppv(B) was 74%. In group C (P30L, V281L, P453S in homozygous or compound heterozygous form with a more severe mutation), ppv(C) was 64.7% to exhibit the nonclassical form of CAH, but 90% when excluding the P30L mutation. Thus, in general, a good genotype-phenotype relationship is shown in patients with either the severest or the mildest mutations. A considerable degree of divergence is observed within mutation groups of intermediate severity. As yet undefined factors modifying 21-hydroxylase gene expression and steroid hormone action are likely to account for these differences in phenotypic expression.

Comprehensive analytical strategy for mutation screening in 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disease with a wide range of clinical manifestations. It is most often caused by deficiency of steroid 21-hydroxylase, reflecting any of a wide range of mutations in the 21-hydroxylase (CYP21) gene. A major challenge in molecular diagnostics of CAH is the high homology between the CYP21 gene and the CYP21P pseudogene and the phenomenon of apparent gene conversion, which inactivates the functional gene. In this study we devised an improved stepwise diagnostic procedure involving nonradioactive Southern blotting and direct DNA sequencing. This strategy led to a successful elucidation of the molecular cause of the disease in 181 out of 182 unrelated alleles in a total of 91 clinically and biochemically characterized patients. We were able to identify all classical known disease-causing mutations of the 21-hydroxylase gene and a novel nonsense mutation (bp 670, A-->C, Y97X). Our method also allows the reliable, secure diagnosis of the heterozygous configuration and may therefore be used for pre-, peri-, and postnatal diagnosis of CAH, even when informative data of the index patient are lacking. Furthermore, it can be used to confirm the diagnosis of CAH in newborns detected in 17-hydroxyprogesterone screening programs.