21 - Hydroxylase Mutation Test

Purpose of the Test

The prenatal diagnosis of the mutations will help in management of the newborn and in preparation of family for the medical and social issues identified with CAH

Background

21-hydroxylase deficiency is the most common form of Congenital Adrenal Hyperplasia (CAH) that results in impaired synthesis of cortisol from cholestrol by adrenal cortex. Inactivating mutations in the 21-hydroxylase gene will help identify various forms of 21-OH deficient CAH. Severe deficiency of the enzyme leads to classical form of Pediatric virilizing phenotype resulting in simple virilizing (25%) or Salt-Wasting (75%). A non-classic form has mild enzyme deficiency demonstrate post-natal onset.

A panel of nine common mutations can identify about 80-98% of cases of alleles responsible for the disease. Sequencing of the entire coding region of the gene along with the flanking intronic region can identify these common mutation and other rarer alleles.

Exception

Not all cases of CAH are caused by 21-OH deficiency; therefore an absence of 21-OH mutations does not definitely prove absence of CAH.

Test Method

PCR and sequencing of the 21-hydroxylase coding exons and flanking splice sites from the patient derived Blood and DNA.

Sample Requirements

We require 2-5ml of blood collected in EDTA containing tubes. Blood should be shipped within 48 hours after collection of blood on ice. You may send 10ug of genomic DNA derived from blood or Chorionic Villus Sampling (CVS), prepared using a Qiagen blood DNA preparation kit (or equivalent) and should have a A260/A280 value of 1.8.

References

Phyllis W. Speiser, M.D., and Perrin C. White, M.D. Congenital Adrenal Hyperplasia. N Engl J Med. 349 (8); 776–788 (2003).

Paola Concolino*, Enrica Mello, Cecilia Zuppi and Ettore Capoluongo, Molecular diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency: an update of new CYP21A2 mutations. Clin Chem Lab Med; 48(8); 1057–1062 (2010).

Anna Wedell. Molecular Genetics of 21- Hydroxylase Deficiency; Endocr Dev. Basel, Karger, vol 20, pp 80–87 (2011).

R. Menassa,* V. Tardy,* F. Despert, C. Bouvattier-Morel, J. P. Brossier, M. Cartigny, and Y. More. p.H62L, a Rare Mutation of the CYP21 Gene Identified in Two Forms of 21-Hydroxylase Deficiency; J Clin Endocrinol Metab. 93 (5): 1901–1908 (2008).

V. Tardy,* R. Menassa,* V. Sulmont, A. Lienhardt-Roussie, C. Lecointre,R. Brauner, M. David, and Y. More. Phenotype-Genotype Correlations of 13 Rare CYP21A2 Mutations Detected in 46 Patients Affected with 21-Hydroxylase Deficiency and in One Carrier. J Clin Endocrinol Metab. 95(3): 1288–1300 (2010)