Background-Aim: Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders caused by defects in the steroidogenic pathway of the adrenal cortex. In their most severe forms, they produce adrenal insufficiency and virilization of external genitalia when involving the terminal enzymes of the cortisol and aldosterone synthesis pathway (21-hydroxylase (21-OHD, OMIM#201910) and 11-hydroxylase (11-OHD, OMIM#202010) deficiencies). Mutations of CYP21A2 gene (Cr6p21.33) account for 95% of cases, meanwhile mutations in CYP11B1 (Cr8q24.3) are the second cause (3-5% of cases). It is characterized by an accumulation of 11-deoxycorticosterone (DOCA) with mineralocorticoid activity. Both genes have tandem homologous regions, CYP21A2 (CYP21A1P pseudogene) and CYP11B1 (CYP11B2 gene), therefore specific molecular approaches are required. We describe a newborn with CAH whose genotyping was useful in the clinical management.
Case Presentation: Newborn from a consanguineous family with extremely virilized external genitalia: thin micropenis, bilateral cryptorchidism and hyperpigmented scrotal sacs. QF-PCR and karyotype: 46XX. Biochemical parameters: Testosterone 14.60ng/mL; 17-OHP 17.31nmol/L; cortisol 3.4μg/dL; DHEA-S 5.57μg/mL; androstenedione >10ng/mL; aldosterone 982pg/mL. Treatment with hydrocortisone and fludrocortisone was started. No salt wasting was evidenced. An embryonal rhabdomyosarcoma with bone marrow and regional lymph nodes infiltration was detected at 5 months.
Molecular Analyses Molecular analyses were performed by gene-specific PCR followed by Sanger sequencing of the overlapping fragments of CYP21A2 and CYP11B1. Allele-specific oligonucleotide (ASO) hybridizations and gene doses analysis by MLPA were done to detect the recurrent alterations of CYP21A2. Allele segregation was established through parental DNA analyses.
Results: CYP21A2 genotyping detected non-severe alleles: c.955C>T (P.Gln319*) in a gene duplicated allele and c.844G>T (P.Val282Leu) in compound heterozygosity. CYP11B1 analysis was carried out and a frameshift alteration c.50_51delins (P.Ser17*) that results in stop codon was detected in homozygosity. Both parents, asymptomatic, were found to be carriers. This non-previously described alteration may be considered pathogenic as it is a null variant in a recessive disease with a loss-of-function mechanism. Mineralocorticoid was discontinued. Post-treatment values: DHEA-S 1μg/mL; cortisol 9.9μg/dL; plasma renin activity 9.6ng/mL/h; DOCA 23.0ng/dL and 11-deoxycortisol in the normal range.
Conclusions: The informativity of gene analyses along with a good genotype/phenotype relationship in CAH facilitates the diagnosis, prognosis and treatment adequacy, even in the absence of pretreatment whole biochemical data or when analytical interferences (not infrequent in direct immunoanalyses of steroids in the neonatal period) difficult the interpretation of results. An expert evaluation of molecular findings and their proper stratification is essential when complex genetic loci, reluctant to massive approaches, are investigated.
15 Sep 2022 - 17 Sep 2022