Prenatal diagnosis of congenital adrenal hyperplasia (21-hydroxylase deficiency) in Croatia

Ethnic-specific distribution of mutations in 716 patients with congenital adrenal hyperplasia owing to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) occurs worldwide. The most common mutations in the CYP21A2 gene in 716 unrelated patients were analyzed and the mutations were grouped by ethnicity, as defined through self-declaration corroborated by review of pedigrees extending to two or three generations. Prevalent allelic mutations and genotypes were found to vary significantly among ethnic groups, and the predominance of the prevalent mutations and genotypes in several of these populations was significant. There are ethnic-specific mutations in the CYP21A2 gene. A large deletion is prevalent in the Anglo-Saxons; a V281L (1685 G to T) mutation is prevalent in Ashkenazi Jews; an R356W (2109 G to A) mutation is prevalent in the Croatians; an IVS2 AS -13 (A/C to G) mutation is prevalent in the Iranians and Yupik-speaking Eskimos of Western Alaska; and a Q318X (1994 C to T) mutation is prevalent in East Indians. Genotype/phenotype non-correlation was seen when at least one IVS2 AS -13 (A/C to G) mutation in the CYP21A2 gene was present.

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency

More than 90% of cases of congenital adrenal hyperplasia (CAH, the inherited inability to synthesize cortisol) are caused by 21-hydroxylase deficiency. Females with severe, classic 21-hydroxylase deficiency are exposed to excess androgens prenatally and are born with virilized external genitalia. Most patients cannot synthesize sufficient aldosterone to maintain sodium balance and may develop potentially fatal "salt wasting" crises if not treated. The disease is caused by mutations in the CYP21 gene encoding the steroid 21-hydroxylase enzyme. More than 90% of these mutations result from intergenic recombinations between CYP21 and the closely linked CYP21P pseudogene. Approximately 20% are gene deletions due to unequal crossing over during meiosis, whereas the remainder are gene conversions--transfers to CYP21 of deleterious mutations normally present in CYP21P. The degree to which each mutation compromises enzymatic activity is strongly correlated with the clinical severity of the disease in patients carrying it. Prenatal diagnosis by direct mutation detection permits prenatal treatment of affected females to minimize genital virilization. Neonatal screening by hormonal methods identifies affected children before salt wasting crises develop, reducing mortality from this condition. Glucocorticoid and mineralocorticoid replacement are the mainstays of treatment, but more rational dosing and additional therapies are being developed.

Congenital adrenal hyperplasia: molecular genetics and alternative approaches to treatment

Several autosomal recessive disorders affecting the adrenal cortex and its development and leading to defective cortisol biosynthesis are known under the collective term "congenital adrenal hyperplasia" (CAH). Over the last two decades, the genes causing most of these disorders have been identified and molecular genetics may supplement their clinical and biochemical diagnosis. In addition, new treatments have emerged; although gene therapy has yet to be applied in humans, studies are ongoing in gene transfer in adrenocortical cell lines and animal models. In this review, after a brief introduction on the developmental biology and biochemistry of the adrenal cortex and its enzymes, we will list the new developments in the genetics and treatment of diseases causing CAH, starting with the most recent findings. This order happens to follow adrenal steroidogenesis from the mitochondrial entry of cholesterol to cortisol synthesis; it is unlike other presentations of CAH syndromes that start with the most frequently seen syndromes, because the latter were also the first to be investigated at the genetic level and have been extensively reviewed elsewhere. We will start with the latest syndrome to be molecularly investigated, congenital lipoid adrenal hyperplasia (CLAH), which is caused by mutations in the gene coding for the steroidogenic acute regulatory (StAR) protein. We will then present new developments in the genetics of 3-beta-hydroxysteroid dehydrogenase (3 beta HSD), 17 hydroxylase and 17,20-lyase (P450c17), 11 hydroxylase (P450c11 beta), and 21 hydroxylase (P450c21) deficiencies. Alternative treatment approaches and gene therapy experiments are reviewed collectively in the last section, because they are still in their infantile stages.