Genetic characterization of a large cohort of Argentine 21-hydroxylase Deficiency

Genetic Characterization of a Cohort of Italian Patients with Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency

INTRODUCTION

Defects in the steroid 21-hydroxylase gene (CYP21A2) cause 21-hydroxylase deficiency (21OHD), the main cause of congenital adrenal hyperplasia (CAH). The disease shows a broad spectrum of clinical forms, ranging from severe or classical (salt wasting, SW, and simple virilizing, SV), to mild late onset or nonclassical (NC). 21OHD affects 1 in 15,000 in its severe classic form and 1 in 200-1000 in its mild NC form. There are many studies reporting the frequency of CYP21A2 pathogenic variants in different populations; however, few of them provide comprehensive information about Italian patients. Here, we present genetic results from a cohort of 245 unrelated Italian individuals with clinical diagnosis of CAH due to 21OHD.

METHODS

A specific polymerase chain reaction (PCR) protocol combined with Sanger sequencing was used for CYP21A2 analysis. The multiplex ligation-dependent probe amplification (MLPA) assay was employed for copy number variation (CNV) determination.

RESULTS

One hundred fourteen (46.5%) of the index cases had the NC form, 57 (23.3%) had the SV form, and 74 (30.2%) presented the SW form of the disease. The most prevalent variant found in NC patients was the p.Val282Leu (51.3%), while the most frequent variants in the classical form were p.Ile173Asn (8.6%) and c.293-13C>G (26.0%). In our study, the frequency of large rearrangements was 15.3%, with CAH-X alleles representing 40% of all DEL/CONV. In addition, 12 alleles carried rare variants, and 1 had a novel variant p.(Arg342Gln). We observed phenotype-genotype correlation in 94.7% of cases. A complete concordance was observed in Groups 0 (enzyme activity completely impaired) where all patients had the SW form as expected. In Group A (0-1% residual enzyme activity), 78.4% of patients had the anticipated SW form while 21.6% were diagnosed with the SV form. Within Group B (~ 2% residual enzyme activity), 93.4% of patients exhibited SV form and 6.5% SW disease. Finally, 92.6% and 7.4% of patients belonging to Group C (enzyme partially impaired to ~ 20-60% residual activity) exhibited NC and SV phenotypes, respectively.

CONCLUSION

This work, representing a comprehensive genetic study, expanded the CYP21A2 variants spectrum of Italian patients with 21OHD and could be helpful in prenatal diagnosis and genetic counseling.

Congenital adrenal hyperplasia with homozygous and heterozygous mutations: a rare family case report

BACKGROUND

Congenital adrenal hyperplasia (CAH), characterized by defective adrenal steroidogenesis, is transmitted in an autosomal recessive manner. Mutations in the steroid 21-hydroxylase gene CYP21A2 causing steroid 21-hydroxylase deficiency account for most cases of CAH. The c.145l-1452delGGinsC gene mutation is rare, and only one case has been reported, but the form of gene mutation is different from this case, resulting in different clinical phenotype. The most common pathogenic genotype of CAH is a homozygous or compound heterozygous mutation, but CAH patients homozygous for the p.I173N mutation and heterozygous for the c.1451-1452delGGinsC mutation have not been reported previously. We report herein a familial case of CAH, in which both siblings carry the rare homozygous p.I173N mutation and heterozygous c.1451-1452delGGinsC mutation.

CASE PRESENTATION

The proband showed amenorrhea, infertility, polycystic ovaries, and increased levels of androgen, rather than the typical clinical manifestations of CAH such as an adrenal crisis or masculine vulva, so was misdiagnosed with polycystic ovary syndrome for many years. Following a correct diagnosis of CAH, she was given glucocorticoid treatment, her menstruation became more regular, and she became pregnant and delivered a healthy baby girl.

CONCLUSIONS

The genotypes may be p.I173N homozygous or p.I173N/c.1451-1452delGGinsC heterozygous, both mutations could be pathogenic. This complex combination of mutations has not been reported or studied before. Through the report and analysis of this genotype, the content of CAH gene bank is enriched and the misdiagnosis rate of CAH is reduced.

Molecular Analysis of 21-Hydroxylase Deficiency Reveals Two Novel Severe Genotypes in Affected Newborns

BACKGROUND AND OBJECTIVE

Congenital adrenal hyperplasia involves a series of autosomal recessive disorders where adrenal steroidogenesis is affected. We present a detailed molecular investigation of 13 newborns affected from the severe form of congenital adrenal hyperplasia related to 21-hydroxylase deficiency.

METHODS

All patients were diagnosed with classical congenital adrenal hyperplasia in the neonatal period due to adrenal crisis and/or ambiguous genitalia presentation. None of the infants was identified through a congenital adrenal hyperplasia newborn screening program. A molecular analysis of the CYP21A2 gene and a familiar segregation analysis were performed.

RESULTS

Adrenal crisis was the most severe manifestation in the male salt-wasting newborns while all female patients presented with atypical genitalia. Newborns were correctly genotyped and no genotype-phenotype divergences were found. Two novel severe genotypes, not previously reported, were identified. The novel CYP21A2 frameshift mutations (c.793delG and c.297dupG) were added to the other 45 variants recently reported in the literature, leading to a total count of 279 pathogenic variants affecting the gene.

CONCLUSIONS

We have successfully genotyped 13 infants diagnosed with classical congenital adrenal hyperplasia after birth. Our molecular approach led to the identification of two novel frameshift CYP21A2 pathogenic variants related to the salt-wasting form of congenital adrenal hyperplasia.