Erroneous prenatal diagnosis of congenital adrenal hyperplasia owing to a duplication of the CYP21A2 gene.

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder where steroidogenesis in the adrenal cortex is impaired. The most common form is caused by 21-hydroxylase deficiency (21OHD). Classical 21OHD is characterized by glucocorticoid and mineralocorticoid deficiency and by overproduction of adrenal androgens. The diagnosis rests on biochemical and genetic analyses. In families with history of CAH, prenatal genetic diagnosis is offered. We herein present a case of an infant whose parents were identified to carry mutations on the CYP21A2 gene. The fetal DNA analysis demonstrated that the fetus carried a paternal exon 8 (Q318X) mutation and a maternal exon 8 (R356X) mutation. The fetus was presumed to be affected with CAH, yet his clinical presentation at birth was not consistent with the diagnosis. Repeated genetic analysis identified a paternal CYP21A2 gene duplication with Q318X mutation on one copy of CYP21A2. We conclude that a duplication of the CYP21A2 gene should be suspected when clinical and hormonal findings do not support the genetic diagnosis. Furthermore, because individuals with Q318X mutation frequently have a duplication of the CYP21A2 gene, when Q318X is detected, it is important to distinguish the severe point mutation in single gene copy alleles from the non-deficient variant in gene-duplicated alleles.

The importance of ß globin deletion analysis in the evaluation of patients with ß thalassemia.

INTRODUCTION: Beta globin deletion/duplication analysis may serve as a useful adjunct to sequence analysis. Our purpose was to develop a robust assay for beta globin deletion/duplication analysis and determine its role in evaluating patients with beta thalassemia. METHODS: A single tube semi-quantitative fluorescent PCR assay capable of detecting deletions and duplications in the beta globin cluster and the associated locus control region (LCR) was developed and validated. RESULTS: Six hundred seventy one de-identified samples submitted for beta globin sequence analysis were tested for deletions and duplications of the beta globin cluster. Twenty-two deletions were detected (3%, 22/671). Seventeen of the 22 (82%) deletion samples were negative for mutations in the whole gene sequencing assay. For 5 of the samples, homozygous point mutations were inferred by beta globin sequencing. Among the deletions detected, 11 (50%) involved only the beta globin gene (5 covering the entire gene, 2 spanning the 5' end of the gene and 4 encompassing the 3' end of the gene). Ten samples (45%) were heterozygous delta-beta deletions spanning both the delta globin and beta globin genes. One patient with a single deletion had Hb Lepore. CONCLUSION: Beta globin deletion/duplication analysis is necessary to correctly identify the genotype in some patients being evaluated for beta thalassemia.