Implications of CYP21A2 gene duplications in carrier screening and prenatal diagnosis of congenital adrenal hyperplasia due to 21 Hydroxylase deficiency

Background: Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder that presents as salt wasting or simple virilization (SV). It is due to biallelic mutations in the CYP21A2 gene that encodes the 21-hydroxylase enzyme. This gene is susceptible to deletions and duplications due to the presence of a homologous pseudogene and its location in the RCCX module. This complicates the interpretation of molecular analysis of the CYP21A2 gene. Clinical Description: During preconception counseling and subsequent workup of a couple, the wife (who had been diagnosed with simple virilizing CAH at the age of 14 years, based on clinical and metabolic profile) was identified with c.373C >T variant on one and a deletion on the other allele of CYP21A2. Her asymptomatic husband harbored a novel c. 939+5G>A variant in intron 7 of CYP21A2. Prenatal diagnosis by Sanger sequencing revealed the presence of both maternal (c.373C>T) and paternal (c. 939+5G>A) variants in the fetus, indicative of SV form. After genetic counseling, the parents decided to continue with the pregnancy. Management and Outcome: A baby boy was born who underwent investigations according to the standard protocol. However, a diagnosis of CAH could not be established conclusively. The molecular diagnosis of both baby and parents was revisited. It was found that the baby harbored a duplication of CYP21A2 (inherited from his father) along with a novel variant. The duplication neutralized the paternal variant, and thus the baby was not affected, but a carrier. Conclusion: Evaluation of duplication in parents is crucial before prenatal testing, as duplications have important bearing on the carrier status

Prevalence of the triple X syndrome in phenotypically normal women with premature ovarian failure and its association with autoimmune thyroid disorders

Objective: To determine the prevalence of triple X femailes among patients with premature ovarian failure and to describe the clinical features of the syndrome. Design: Case report. Setting: Tertiary care hospital. Patient(s): Fifty-two consecutive patients with secondary amenorrhea due to premature ovarian failure and no clinical stigmata of Turner's syndrome. Main outcome measure(s): Triple X syndrome and clinical features, as assessed by karyotype analysis using Giemsa trypsin banding of metaphase chromosomes. Result(s): Two of the 52 patients with premature ovarian failure had triple X syndrome. Both cases had associated autoimmune thyroid disorder. One of the women with triple X syndrome had two pregnancies that were complicated by premature birth, idiopathic thrombocytopenia, neonatal death, and occipital encephalocoele. Conclusion(s): Among patients with premature ovarian failure, 3.8% have triple X syndrome. The syndrome may be associated with autoimmune thyroid disorder and poor pregnancy outcome due to congenital malformation

Prenatal diagnosis of steroid 21-hydroxylase-deficient congenital adrenal hyperplasia: Experience from a tertiary care centre in India

Background & objectives: Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder with a wide range of clinical manifestations. The disease is attributed to mutations in CYP21A2 gene encoding 21-hydroxylase enzyme. In view of severe phenotype in salt-losing cases, issues related to genital ambiguity in girls and precocity in boys, most families opt for prenatal testing and termination of affected foetus. CAH can be diagnosed in utero through direct molecular analysis of CYP21A2 gene, using DNA extracted from foetal tissues or cells obtained from chorionic villus sampling or amniocentesis. The objective of this study was to evaluate the feasibility and accuracy of prenatal diagnosis (PND) using sequencing and multiplex ligation probe amplification (MLPA) methods in families at risk for CAH. Methods: Fifteen pregnant women at risk of having an affected offspring with CAH were included in this study. Ten families had previous affected children with salt-wasting/simple virilising form of CAH and five families did not have live children but had a high index of suspicion for CAH in previous children based on history or records. Mutation analysis was carried out by Sanger sequencing and MLPA method. Results: Seven different mutations were identified in 15 families. Deletions and I2g mutation were the most common. Of the 15 foetuses analyzed, nine were unaffected while six were affected. Unaffected foetuses were delivered, they were clinically normal and their genotype was found to be concordant to the prenatal report. All except two families reported in the second trimester. None of the couples opted for prenatal treatment. Interpretation & conclusions: Our preliminary findings show that PND by direct mutation analysis along with MLPA is a feasible strategy that can be offered to families at risk