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

• Analysis of two families with no CAH genotype–phenotype correlation
• Association of direct sequencing, MLPA and enzymatic restriction methods
• Validation of a previous process for trimodular RCCX haplotype identification
• Use of this molecular approach to clarify ambiguous cases of CAH

ContextCongenital 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.ObjectivesWe 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 methodsTo 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.ResultsThe 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.ConclusionsThe strategy suggested is useful to facilitate molecular testing in CAH patients, considering the new evidence about possible different haplotypes.