Characterization of steroid 21-hydroxylase gene mutations in a oligosymptomatic form of congenital adrenal hyperplasia: family study

BACKGROUND: 21-hydroxilase deficiency accounts for over 90% of all cases of congenital adrenal hyperplasia (CAH). There is a non-negligible incidence of both severe and nonclassical forms of this genetic disorder. Enzyme deficiency is due to mutations in the gene encoding adrenal 21-hydroxylase (named CYP 21B) and is inherited in an autosomical recesive way. Complete or partial impairment of enzyme activity has been correlated with the different clinical forms of the disease. PATIENTS AND METHODS: In the present paper CYP 21B gene analysis results obtained in a family with two kindred affected by a nonclassical form of the disease are shown. Clinical assessment of these two kindred showed a very mild form of the disease, whereas biochemical results suggested a late-onset partial 21-hydroxylase deficiency. Genotyping for deletions and 10 point mutations in the CYP 21B gene was performed by Southern blot analysis and polymerase chain reaction (PCR) allele-specific oligonucleotide (ASO) hybridation technique. RESULTS: Molecular genetic analysis performed in the two affected patients and two further relatives allowed us to detect the presence of different mutations in the two alleles of the CYP 21B gene. One of these mutations was severe (655G) and came from maternal line, whereas the other was mild (Val281Leu) and originated in paternal line. CONCLUSION: Molecular genetic analysis allows the possibility of finding severe (and non-expected) mutations in patients with clinically mild and late-onset forms of the 21-hydroxylase deficiency.     

Molecular genotyping in Brazilian patients with the classical and nonclassical forms of 21-hydroxylase deficiency

The aim of our study was to determine, by allele-specific PCR, the frequency of point mutations in 130 Brazilian patients with the classical and nonclassical forms of 21-hydroxylase deficiency and to correlate genotype with phenotype. The most frequent mutations were 12 splice (41.8% in salt wasting), I172N (32.6% in simple virilizing), and V281L (40.2% in late onset form). The frequency of the 9 most common point mutations was similar to that reported for other countries, except for Del 8 nt and Cluster, which were less frequent in the classical form. Rarer mutations such as P453S, G291S, I7 splice, W405X, R483P, and R483-->frameshift were rarely found or were absent. The 93 fully genotyped patients were classified into 3 mutation groups, based on the degree of enzymatic activity (group A, <2%; group B, approximately 2%, and group C, >18%). In group A, 62% of the cases presented the salt wasting form; in group B, 96% the simple virilizing form; and in group C, 88% the late onset form. We diagnosed 80% of the affected alleles after screening for large rearrangements and 15 point mutations. The absence of previously described mutations in 20% of the affected alleles suggests the presence of new mutations in our population.     

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.     

Congenital adrenal hyperplasia in pregnancy

The congenital adrenal hyperplasias (CAH) are a group of inherited enzymatic defects of adrenal steroid biosynthesis. Deficiencies of each enzyme required in the steroid biosynthesis pathway are known, and these deficiencies are all inherited as autosomal recessive disorders. During pregnancy, maternal and fetal problems are confined to women who have 21-hydroxylase deficiency (P450c21 deficiency), 11-hydroxylase deficiency (P450c11 deficiency), and 3 beta-hydroxysteroid dehydrogenase deficiency (3 beta HSD deficiency), because other adrenal enzyme deficiencies are not compatible with fertility. The interposition of the placenta on the hypothalamic-pituitary-adrenal axis and other endocrine changes during pregnancy impact considerably on the clinical evaluation of the congenital adrenal hyperplasias. Successful management of CAH in pregnancy requires a firm knowledge of normal adrenal anatomic and endocrine changes that occur during gestation. Women with severe forms of CAH have decreased fertility rates because of oligo-ovulation, and successful conception requires a combination of good therapeutic compliance, careful endocrine monitoring, and often ovulation induction. From a fetal and neonatal standpoint, accurate prenatal diagnosis of 21-hydroxylase deficiency and 11-hydroxylase deficiency is now possible, which allows for prenatal treatment in an attempt to minimize clinical problems in the neonates. Prevention of masculinization of affected female fetuses by corticosteroid suppression has been attempted in both 21-hydroxylase deficiency and 11beta-hydroxylase deficiency CAH, with variable degrees of success. This review provides an overview of the congenital adrenal hyperplasias and their management during pregnancy.     

Mucoepidermoid carcinoma arising in Warthin''s tumour of the parotid gland: report of two cases with histopathological, ultrastructural and immunohistochemical studies

OBJECTIVE: To study the molecular defects of congenital adrenal hyperplasia (CAH). STUDY DESIGN: Twenty Chinese patients, including 8 with salt-wasting (SW) type CAH, 11 with simple virilizing (SV) type CAH and 1 with nonclassical (NC) type CAH, were recruited. Two rounds of the polymerase chain reaction (PCR) were used to study the 21-hydroxylase gene (CYP21). The primary PCR amplified CYP21-specific DNA fragments, and the secondary PCR used products from the primary PCR for analysis of amplification-created restriction sites (ACRS) and direct DNA sequencing. In all patients, ACRS analysis was done at 12 possible mutation sites, and then direct DNA sequencing was performed to confirm or define the molecular defects. RESULTS: Ten different mutations, including nine point mutations and gross gene deletion or conversion, were found in this study. Of the nine point mutations, eight could be easily detected by ACRS analysis. The three most common mutations were codon (CD)172 t-->a (I172N), IVS-II 656 c/a-->g, and gross gene deletion or conversion, accounting for 27.5% (11/40 alleles), 25% (10/40) and 20% (8/40) of all identified mutations, respectively. All SW patients were compound heterozygotes of IVS-II 656, gross gene deletion or conversion, or other severe defects, including CDs236 (t-->a) (I236N)+ 237 (t-->a) (V237E)+ 239 (t-->a) (M239K), CD306 (+t), CD318 (c-->t) (Q318X) and CD356 (c-->t) (R356W) mutations. All SV patients had one allele with a CD172 (I172N) mutation. One allele of an NC patient had a CD183 (c-->g) (D183E) mutation, and the other allele was not defined. In the whole series, four alleles (10%) had more than one mutation. CONCLUSION: We found 10 different mutations in this study. The correlation between genotypes and phenotypes was compatible with the reported data. Two rounds of PCR and ACRS analysis may provide important information for genetic counseling, prenatal diagnosis and management of families at risk for CAH.     

Androgen-related effects on peripheral glucose metabolism in women with congenital adrenal hyperplasia

The study was designed to investigate the influence of androgens on peripheral glucose metabolism in women with congenital adrenal hyperplasia (CAH). Nine normal women and seven women with CAH were studied (4 with the classical form of 21-hydroxylase deficiency [C 21-OH] and 3 with nonclassical 21-hydroxylase deficiency [NC 21-OH]). The study was performed using the forearm model combined with local indirect calorimetry. The insulin level reached 30 minutes after glucose ingestion was significantly greater (p < .05) in patients with CAH. The patients with C 21-OH had elevated androstenedione (A) and testosterone (T) and low DHEA-S and presented a 35% greater insulin response to a glucose stimulus than the control group, area under the curve (AUC) of 9457 +/- 887 vs 6989 +/- 833 microU/ml.3 hours. Patients with NC 21-OH had slightly elevated T, A and DHEA-S and presented an insulin response that was similar to the control group, AUC = 7208 +/- 1935 microU/ml.3 hours. Despite the greater muscle mass of the patients with CAH the forearm glucose uptake during the three hours of the study was lower in these patients than in normal women (CAH = 100.9 +/- 10.0 vs control group = 132.5 +/- 21.2 mg/100 ml forearm). The ratio of insulin response to the increment of forearm glucose uptake over a period of 3 h was significantly higher in patients with CAH (control group = 59.6 +/- 6.5 vs CAH = 98.6 +/- 19.4 microU.ml-1/mg.100 ml forearm-1, p < 0.05). These results suggest that insulin sensitivity is decreased in patients with CAH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Congenital adrenal hyperplasia (21-hydroxylase deficiency) without demonstrable genetic mutations

Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency (21-OHD) is the most common inherited defect of adrenal steroid biosynthesis. At least 36 mutations in the CYP21 gene, which is mapped to chromosome 6p21.3, have been described. We performed genetic analysis of the CYP21 gene in a patient with classic 21-OHD CAH and her family. The entire exonic coding regions and intronic regions, as well as the -1 kb 5' upstream promoter region, were thoroughly sequenced and analyzed. Despite extensive sequencing, no mutation was found in this 3.7 kb area. The 11beta-hydroxylase defect, closely mimicking the clinical and biochemical phenotype of classic 21-OHD, was excluded by directly sequencing 2.6 kb covering the entire coding of the CYP11B1 gene. Herein we describe a phenotypically and hormonally affected patient with classic simple virilizing 21-OHD CAH who lacks a mutation in the entire CYP21 gene and coding region of the CYP11B1 gene.     

High frequency of nonclassical steroid 21-hydroxylase deficiency

Nonclassical steroid 21-hydroxylase deficiency is an autosomal recessive disorder that is defined by clinical and hormonal criteria that distinguishes it from the classical 21-hydroxylase deficiency. No estimates of the gene frequency of nonclassical 21-hydroxylase deficiency, also called attenuated, late-onset, acquired, and cryptic adrenal hyperplasia, have been published thus far. Here, we have used HLA-B genotype data in families containing multiple members affected with nonclassical 21-hydroxylase deficiency together with the results of quantitative hormonal tests to arrive at estimates of gene and disease frequencies for this disorder. We found nonclassical 21-hydroxylase deficiency to be a far more common disorder than classical 21-hydroxylase deficiency, which occurs in 1/8,000 births. The prevalence of the disease in Ashkenazi Jews was 3.7%; in Hispanics, 1.9%; in Yugoslavs, 1.6%; in Italians, 0.3%; and in the diverse Caucasian population, 0.1%. The gene for nonclassical 21-hydroxylase deficiency is in genetic linkage disequilibrium with HLA-B14 in Ashkenazi Jews, Hispanics, and Italians, but not in Yugoslavs or in a diverse, non-Jewish, Caucasian group. The penetrance of nonclassical 21-hydroxylase deficiency gene in the HLA-B14 containing haplotypes was incomplete. Thus, nonclassical 21-hydroxylase deficiency is probably the most frequent autosomal recessive genetic disorder in man and is especially frequent in Ashkenazi Jews, Hispanics, Italians, and Yugoslavs.     

CGH-detected DNA sequence copy number amplifications can be confirmed by interphase-FISH: new possiblities for prognostic approaches in oral squamous cell carcinomas

OBJECTIVE: Following the observation of two patients affected by true precocious puberty who went on to develop polycystic ovary syndrome (PCOS) and who were found to be heterozygotes (carriers) for 21-hydroxylase deficiency (21-OHD), we decided to evaluate the frequency of heterozygosity for adrenal 21-OHD in patients with true precocious puberty. STUDY DESIGN: We investigated 32 girls affected by true precocious puberty, by the single-dose ACTH stimulation test, HLA typing and the molecular analysis of the CYP21B gene encoding for the 21-OH enzyme, in order to detect gene deletions or point mutations. Twenty-eight cases were on LHRH analogue treatment and the remaining four, untreated owing to parental refusal, were investigated 0.5-1.5 years after spontaneous menarche. RESULTS: After ACTH testing, 13 out of the 32 (41%) cases displayed higher 17-hydroxyprogesterone (17-OHP) levels than normal but less than those found in patients affected by nonclassical adrenal hyperplasia (CAH); these levels were similar to those observed in obligate heterozygotes for CAH due to 21-hydroxylase deficiency (21-OHD). HLA typing showed a significantly increased frequency of the HLA alleles A28 and B14 which are peculiar to the HLA haplotypes of nonclassical CAH due to 21-OHD. Molecular analysis of the CYP21B gene showed that in four out of the 10 tested patients with an exaggerated 17-OHP response there were heterozygous point mutations of the CYP21B gene. In contrast, no CYP21B gene abnormalities were detected in the eight tested patients with normal 17-OHP. No differences were found between carriers and non-carriers of the 21-OHD with regard to age at onset of precocious puberty, clinical features, bone age acceleration and gonadal suppression induced by LH-RH analogue treatment. Two out of the four untreated patients who were investigated after menarche were found to be carriers of the 21-OHD; these girls showed signs of androgen excess, irregular menses and polycystic ovaries. CONCLUSIONS: A high frequency of heterozygosity for adrenal steroid 21-OHD was found in our patients with true precocious puberty. This adrenal defect does not seem to influence the pattern of central precocious puberty, but these patients require long-term follow-up as they might go on to develop polycystic ovary syndrome (PCOS). Whether or not heterozygosity of the 21-OHD may be related to the premature activation of the hypothalamo-pituitary-gonodal axis remains to be defined.     

Rapid screening method for detecting mutations in the 21-hydroxylase gene

Impaired synthesis of adrenal steroid hormones because of steroid 21-hydroxylase deficiency is one of the most common inborn errors of metabolism. To expedite molecular diagnosis in families with 21-hydroxylase deficiency, we have designed a rapid strategy to determine nine of the most common mutations in the 21-hydroxylase gene. According to the mutation to be detected, we apply either of two simple strategies: digestion with adequate restriction enzyme or use of the amplification-created restriction site (ACRS) approach and subsequent restriction analysis. Both procedures are rapid and, being nonradioactive, are safer to perform; moreover determination of zygosity in the analyzed mutations requires only one tube per mutation.     

Uniparental disomy for chromosome 6 results in steroid 21-hydroxylase deficiency: evidence of different genetic mechanisms involved in the production of the disease

Congenital adrenal hyperplasia (CAH) is an inherited recessive disorder of adrenal steroidogenesis caused by mutations in the steroid 21-hydroxylase gene (CYP21) in more than 90% of affected patients. The CYP21 gene is located within the HLA complex locus on chromosome 6 (6p21.3). During a molecular characterisation study of a group of 47 Mexican families with 21-hydroxylase deficiency, we identified nine in which the mutation or mutations found in the patient did not appear to originate from one of the parents. Through DNA fingerprinting, paternity was established in all nine families with a probability of non-paternity in the range of 10(-19) to 10(-23). Among these families, we identified one patient with exclusive paternal inheritance of all eight markers tested on chromosome 6p, despite normal maternal and paternal contributions for eight additional markers on three different chromosomes. We did not identify duplication of paternal information for markers in the 6q region, consistent with lack of expression of transient neonatal diabetes owing to genomic imprinting in this patient. Our results substantiate evidence for the existence of different genetic mechanisms involved in the expression of this recessive condition in a substantial portion (approximately 19%) of affected Mexican families. In addition to the identification of a patient with paternal uniparental disomy, the occurrence of germline mutations may explain the unusual pattern of segregation in the majority of the remaining eight families.     

Intermittent cyclical etidronate in the prevention of corticosteroid-induced bone loss

We describe here a unique case of congenital adrenal hyperplasia (CAH) accompanied by Klinefelter syndrome. A Japanese boy was diagnosed as having CAH caused by 21-hydroxylase deficiency at birth, but was untreated thereafter until age 10. In the meantime he showed marked acceleration in somatic growth with sexual precocity by age 9, at which time growth completely stopped. During regular follow-ups at our clinic and steroid treatment after age 10, he was recognized as having bilateral small and firm testes. A chromosomal examination and a testicular biopsy revealed a complication of 47, XXY Klinefelter syndrome with CAH. Association of these two diseases has not been reported so far, and the present case is the first one to our knowledge.     

Induction of beta-cell rest in type 1 diabetes. Studies on the effects of octreotide and diazoxide

We report on two siblings with classic simple virilizing 21-hydroxylase deficiency whose neonatal screening for serum 17alpha-hydroxyprogesterone (17-OHP) gave normal results. The proband, a girl with clitoromegaly whose screening 17-OHP value had been 9.2 ng/ml, was diagnosed at the age of 6 months, and her elder brother with the initial screening level of 15.7 ng/ml was diagnosed at the age of 6 years due to precocious puberty. Although the occurrence of false-negative cases is extremely rare, it can happen in a simple virilizing form of 21-hydroxylase deficiency. This experience informs that normal results for neonatal screening cannot be an excuse for not evaluating siblings of the proband with congenital adrenal hyperplasia.     

Chlormadinone acetate as a possible effective agent for congenital adrenal hyperplasia to suppress elevated ACTH and antagonize masculinization

We report two cases of congenital adrenal hyperplasia (CAH) in which administration of chlormadinone acetate (CMA), a substituted progestational agent for prostatic disease, suppressed ACTH hypersecretion and lowered plasma testosterone levels. Case 1 was 83-year-old male with advanced prostatic carcinoma and CAH due to 21-hydroxylase deficiency. His plasma testosterone did not decrease in spite of a bilateral orchiectomy. Case 2 was 40-year-old female with CAH due to 21-hydroxylase deficiency suffering from virilization after the cessation of cortisol supplement therapy because of her breast carcinoma. In these two cases, oral administration of CMA at a daily dose of 75-100 mg suppressed ACTH and cortisol to subnormal levels and reduced testosterone levels. With the suppressive effect on ACTH excess and antiandrogenic action, CMA may be suitable for patients with CAH suffering from symptoms due to overproduced ACTH or adrenal androgen.     

Premenstrual syndromes

A splicing junction mutation at nucleotide 656 (A-> G substitution, I2G) in the steroid 21-hydroxylase gene (CYP21) is the most frequently detected mutation in patients with the salt-wasting and simple-virilizing forms of steroid 21-hydroxylase deficiency (approximately 60%). In this disease, prenatal diagnosis and treatment to minimize the effects of excess androgen in affected females has been advocated. Therefore, to detect the I2G mutation rapidly, accurately, and without the use of radioisotope, we developed a modified polymerase chain reaction (PCR) with a mismatched 3' nucleotide primer to introduce a new restriction site upon PCR amplification of the mutant allele. This allowed the mutant allele to be identified readily by restriction enzyme digestion of the PCR product, and subsequently this PCR product was subjected to restriction enzyme digestion for diagnosis. Chorionic villus biopsy samples (CVS) were obtained at 10 to 11 weeks gestation from two females carrying fetuses at risk for steroid 21-hydroxylase deficiency. Prenatal diagnosis was successful in both cases. One affected female was treated with dexamethasone to term. In the other case, treatment was withdrawn at an early stage when testing revealed a normal fetus. The results demonstrate the rapid and accurate detection of the I2G mutation by this method, thereby indicating the feasibility of for prenatal diagnosis of the I2G mutation.     

Congenital adrenal hyperplasia presenting as massive adrenal incidentalomas in the sixth decade of life: report of two patients with 21-hydroxylase deficiency

Divergent recommendations exist regarding the evaluation of adrenal incidentalomas. Recent data have indicated a prevalence of adrenal tumors of 71% in nonclassical congenital adrenal hyperplasia (CAH) and unmasked heterozygotes. These data expand the differential diagnosis of such incidental tumors and substantially modify the approach to their evaluation. We present two patients, female pseudohermaphrodites with the simple virilizing form of CAH and 21-hydroxylase deficiency, who functioned successfully as married phenotypic males. Both came to medical attention in the sixth decade by virtue of massive adrenal incidentalomas encountered in the evaluation of recurrent urinary tract infections. Each had a 46, XX karyotype, no palpable testes, and markedly elevated baseline levels of 17-hydroxyprogesterone (17-OH Prog) of 6086 ng/dL and 6750 ng/dL. Both responded appropriately to dexamethasone suppression with reduction of 17-OH Prog, androgens and, in the second patient, ACTH to normal or near normal levels. Histologic and autopsy examination of the first patient's tumor and computed tomographic characteristics of the second revealed a benign adenoma and myelolipoma respectively. We extend and confirm previous recommendations that CAH be included in the differential diagnosis of adrenal incidentaloma and that baseline 17-OH Prog. levels be obtained, with ACTH stimulation if necessary, to diagnose the presence of nonclassical CAH.     

Comparative characteristics of steroidogenesis and its biorhythm in the hyperfunctioning adrenal cortex

The paper summarizes the results od several studies of the daily rhythms of steroid hormones in patients with ACTH-dependent Itsenko-Cushing's disease (CD) and congenital adrenal hyperplasia (late-onset forms) (CAH). Normal daily rhythms of adrenal C21- and C19-steroids and ACTH were observed in 23.5% of CD patients. CAH patients had the marked daily rhythms of adrenal androgens and testosterone which were typical of those of cortisole. The ratios of steroid hormones to its precursors provide evidence for enhanced activities of 17-, 11 beta- and 18-hydroxylases in CD patients and normal enzymatic activities in CAH patients, whereas 21-hydroxylase being an exception.     

Identification of missense mutations and haplotyping of carnitine palmitoyltransferase II gene

Carnitine palmitoyltransferase II(CPTII) deficiency manifests as two different clinical phenotypes: an adult form associated with muscular symptoms and an infantile form presenting with hepatocardiomuscular manifestations. We have investigated three Japanese patients with CPT II deficiency. Molecular analysis revealed two novel missense mutations, a glutamate (174)-to-lyine substitution (E174K) and a phenylalanine (383)-to-tyrosine substitution (F383Y) in the CPTII cDNA. Transfection experiments demonstrated that the two mutations reduced CPTII catalytic activity. We also identified a novel polymorphism in the CPTII gene, a phenylalanine (352)-to-cysteine substitution (F352C). According to an expression analysis this mutation did not alter CPTII activity. It was present in 21 out of 100 normal alleles in the Japanese population, but was not observed among Caucasians. Genotyping with the F352C polymorphism and the previously reported polymorphisms V368I and M647V allowed normal alleles to be classified into five haplotypes. In all three families, the E174K mutation resided only on F1V1M1 allele, while the F383Y mutation was observed on F2V2M1 allele, suggesting a single origin of each mutation.     

Two CPT2 mutations in three Japanese patients with carnitine palmitoyltransferase II deficiency: functional analysis and association with polymorphic haplotypes and two clinical phenotypes

Carnitine palmitoyltransferase II (CPT II) deficiency manifests as two different clinical phenotypes: a muscular form and a hepatic form. We have investigated three nonconsanguineous Japanese patients with CPT II deficiency. Molecular analysis revealed two missense mutations, a glutamate (174)-to-lysine substitution (E174K) and a phenylalanine (383)-to-tyrosine substitution (F383Y) in the CPT II cDNA. Transfection experiments in COS-1 cells demonstrated that the two mutations markedly decreased the catalytic activity of mutant CPT II. Case 1 (hepatic form) was homozygous for the F383Y mutation, whereas case 3 (muscular form) was homozygous for the E174K mutation. Case 2 and her brother, who were compound heterozygotes for E174K and F383Y, exhibited the hepatic phenotype. We also identified a novel polymorphism in the CPT2 gene, a phenylalanine (352)-to-cysteine substitution (F352C), which did not alter CPT II activity in transfected cells. It was present in 21 out of 100 normal alleles in the Japanese population, but absent in Caucasian populations. Genotyping with the F352C polymorphism and the two previously reported polymorphisms, V368I and M647V, allowed normal Japanese alleles to be classified into five haplotypes. In all three families with CPT II deficiency, the E174K mutation resided only on the F1V1M1 allele, whereas the F383Y mutation was observed on the F2V2M1 allele, suggesting a single origin for each mutation.     

Allele-dropout using PCR-based diagnosis for the splicing mutation in intron-2 of the CYP21B-gene: successful amplification with a Taq/Pwo-polymerase mixture

The splicing mutation in intron 2 (nucleotide 656) of the 21-hydroxylase gene (CYP21B) is the most common mutation causing congenital adrenal hyperplasia (CAH). Homozygosity for nt656G is associated with the classical phenotype of CAH. In several studies, a number of clinically asymptomatic relatives of CAH-patients were genotyped as nt656G homozygotes. We have proposed that the putative asymptomatic nt656G/G individuals are incorrectly typed due to dropout of one allele (in most cases nt656C) during PCR amplification. Here, we report the successful amplification of all alleles at nt656 with a Taq/Pwo DNA polymerase mixture in the primary PCR reaction. The results were independent from the type of polymerase used for sequencing reactions as the second step in mutation analysis.