Rapid Molecular Diagnosis Of Congenital Adrenal Hyperplasia Due To 21-hydroxylase Deficiency

Objective 21-Hydroxylase Deficiency(21-OHD)is the most common cause of Congenital Adrenal Hyperplasia(CAH). Although it can be divided into two major phenotypes:classic and non-classic, the majority of the disease is characterized by over-production of androgen and impaired cortisol and aldosterone biosynthesis. Classic form is characterized by virilisation of the external genitalia in newborn females and hyponatremia, hypochloraemia and hyperkalemia. Severely affected newborns are at risk for life-threatening salt-wasting crises if proper medical care is not delivered. Due to the high morbidity and mortality of the classic forms, newborn screening programs that measure serum 17-hydroxyprogesterone(17-OHD) levels are widely used as routine examination. However, because of the high false-positive or false-negative rate, gene analysis has been suggested as second-tier screening in positively tested newborns. The CYP21A2 gene, which encodes a 21-hydroxylase, has a complex structure and is considered one of the most polymorphic of human genes. The high degree of sequence homology and complexity of mutations bring great difficulty to genetic diagnosis. In this research, we aimed at establishing an accurate, rapid and clinically applicable genetic diagnostic system for 21-OHD, through which accurate diagnosis and informative genetic counseling could be provided.Methods Totally, five patients with CAH and their families, and nine 46,XX DSD:the masculinised females were studied dependent Multiplex ligation-dependent probe amplification(MLPA) and specificity PCR sequencing analysis of CYP21A2 gene mutations.Results MLPA confirmed the complete deletion of one CYP21A2 allele in 4 patients and one CYP21A2/CYP21A1P chimera. ten patients' genotypes were identified by combination MLPA with sequencing analysis, in which I172N was the commonest mutation of CAH(SV).Conclusion Combining MLPA with the specific amplification of DNA sequencing is able to detect 21-OHD fast and accurately for clinical.