Lack of genotypephenotype correlation in congenital adrenal hyperplasia due to a CYP21A2-like gene.

Context: Congenital Adrenal Hyperplasia (CAH) due to 21-hydroxylase deficiency, encoded by CYP21A2 gene, is an autosomal recessive disorder. The CYP21A2 gene, localized in a genetic unit defined RCCX module, is considered one of the most polymorphic of human genes.

Objectives: We considered new evidences about the presence of a RCCX trimodular haplotype with a CYP21A2-like gene to explain the lack of a genotype-phenotype correlation in individuals of two different families.

Design And Methods: To verify gene duplication we used Multiplex Ligation Probe-Dependent Amplifications (MLPA) and to confirm the presence of a CYP21A2-like gene downstream TNXA gene we used previously described amplification and restriction strategy followed by the sequencing of the CYP21A2 gene downstream TNXB gene.

Results: The amplification strategy and restriction analysis of CYP21A1P/CYP21A2-TNXA PCR product in association with MLPA assay and sequencing of CYP21A2 gene downstream TNXB were able to identify the presence of the CYP21A2-like gene in healthy subjects of the two families, wherein the direct sequencing of CYP21A2 gene showed genotypes correlated to pathological phenotypes.

Conclusions: The strategy suggested is useful to facilitate molecular testing in CAH patients, considering the new evidence about possible different haplotypes.