Neonatal 17-hydroxyprogesterone levels adjusted according to age at sample collection and birthweight improve the efficacy of congenital adrenal hyperplasia newborn screening

Congenital adrenal hyperplasia (CAH) is one of the most common inherited metabolic disorders. It comprises a group of autosomal recessive disorders caused by the deficiency of one of four steroidogenic enzymes involved in cortisol biosynthesis or in the electron donor enzyme P450 oxidoreductase (POR) that serves as electron donor to steroidogenic cytochrome P450 (CYP) type II enzymes. The biochemical and clinical phenotype depends on the specific enzymatic defect and the impairment of specific enzyme activity. Defects of steroid 21-hydroxylase (CYP21A2) and 11beta-hydroxylase (CYP11B1) only affect adrenal steroidogenesis, whereas 17alpha-hydroxylase (CYP17A1) and 3beta-hydroxysteroid dehydrogenase type 2 (HSD3B2) deficiency also impact on gonadal steroid biosynthesis. Inactivating POR gene mutations are the cause of CAH manifesting with apparent combined CYP17A1-CYP21A2 deficiency. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant: skeletal malformations and severe genital ambiguity in both sexes.

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.

Nonclassical congenital adrenal hyperplasia (NC-CAH) due to partial 21-hydroxylase deficiency is one of the most frequent autosomal recessive diseases. The aim of this study was to determine the genotype/phenotype relationship in probands and family members. A total of 161 NC-CAH unrelated women diagnosed on late-onset symptoms, mainly hirsutism, and post-ACTH 17-hydroxyprogesterone more than 10 ng/ml, and 330 of their relatives was explored. CYP21A2 was genotyped in 124 probands. The most frequent mutation was V281L. One severe mutation was found in 63.7% of probands, and surprisingly two severe mutations in four probands. Contrasting with the absence of clinical differences, basal testosterone, and androstenedione, basal and post-ACTH 17-hydroxyprogesterone were significantly higher in probands carrying at least one severe mutation than in those with two mild mutations (P < 0.01). Among the 330 family members, 51 were homozygotes or compound heterozygotes, and 42 were clinically asymptomatic; 242 were heterozygotes and 37 unaffected. Post-ACTH 21-deoxycortisol (21dF) was significantly higher in heterozygotes than in unaffected, however, an overlap existed. In 12 heterozygotes, post-ACTH 21dF was below 0.55 ng/ml, the cutoff value usually accepted for suggesting heterozygosity. The study of family members underlines the variable expression of NC-CAH even within a family, suggesting that modifier factors may modulate phenotype expression. Post-ACTH 21dF cannot reliably detect heterozygous subjects. Considering the high frequency of heterozygotes in the general population, it is essential to genotype the partner(s) of the patients with one severe mutation to offer genetic counseling.