The prevalence of the non-classical form of congenital adrenal hyperplasia as exemplified (by the population of the Moscow region)

The non-classical form of 21-hydroxylase deficiency (NC21OH) is one of the most common monogenic diseases inherited in the autosomal-recessive pattern. The incidence of this condition in the Russian population, unlike that of its classical variant, remains to be elucidated. Aim. The objective of the present study was to estimate the true incidence of NC21OH based on the prevalence of the two most frequent mutations associated with this disease. A total of 998 randomly selected blood spots were obtained in the course of neonatal screening of the children born within one calendar year at the territory of the Moscow region. The incidence of the disease was calculated with the use of Hardi-Weinberg equation. The minimal prevalence rate of NC21OH in the population of the Moscow region was estimated to be 1:2206. The level of 17-hydroxyprogesterone (17-OHP) calculated based on the results of the screening studies can not be used to identify the carriers of the pathology of interest whereas neonatal screening allows to diagnose no more than 90% of the cases of NC21OH.