Non-classical 21-hydroxylase deficiency in children: association of adrenocorticotropic hormone-stimulated 17-hydroxyprogesterone with the risk of compound heterozygosity with severe mutations.
OBJECTIVE
To investigate the association between levels of 17-hydroxyprogesterone (17-OHP) and the risk of being compound heterozygous for severe mutations in children with non-classical 21-hydroxylase deficiency (NC21OHD).


METHODS
In 86 Spanish NC21OHD children (75 families) an analysis of the 21-hydroxylase (21-OH) gene was performed by CYP21B-specific polymerase chain reaction amplification, allele-specific oligonucleotide hybridization and Southern blotting. Familial analysis established how the alleles segregated, and allowed the selection of 21-OH-genotyped normal and carrier children, which proved useful in determining a more precise definition of the cut-off for diagnosis. Receiver operating characteristics (ROC) curve analyses were performed to determine the potential value of 17-OHP in predicting compound heterozygosity for severe mutations.


RESULTS
Thirty-four of the 86 children (39%) were found to carry one severe 21-OH mutation (7.3% deletions or conversions, 2.7% 655G, 2.7% Q318X, 1.3% 1172N, 1.3% R356W, and 3.3% double microconversions or small conversions involving single exons). The predominant mutation was V281L (56.7%). P453S and P30L were less frequent (3.3 and 2%). No patient showed two severe mutations. The degree of enzymic deficiency, as measured by basal or adrenocorticotropic hormone (ACTH)-stimulated 17-OHP levels in fully genotyped patients, but not clinical severity (age and number of symptoms at diagnosis), was found to be significantly greater in children with the severe/mild genotype. ROC curve analyses revealed a strong association between ACTH-17-OHP and genotype (area under the curve 0.908, SE 0.057).


CONCLUSIONS
ACTH-stimulated 17-OHP may predict the risk of severe mutations in compound heterozygosity in children (maximum predictive value 93% sensitivity and 83% specificity for a cut-off at 151 nmol l(-1)), although a certain overlap in individual values is observed and performance of molecular analysis should never be obviated in the genetic counselling of these patients.
Ezquieta
B
B
Servicio de Bioquímica, Hospital Universitario La Paz, Madrid, Spain. bezquieta@airtel.net
Cueva
E
E
Varela
J
J
Oliver
A
A
Fernández
J
J
Jariego
C
C
D019326:17-alpha-Hydroxyprogesterone / Q000097:blood*; D000312:Adrenal Hyperplasia, Congenital / Q000097:blood* / Q000209:etiology / Q000235:genetics*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000367:Age Factors; D002648:Child; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D009154:Mutation / Q000235:genetics*; D011237:Predictive Value of Tests; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013268:Stimulation, Chemical
D019326:17-alpha-Hydroxyprogesterone; D000324:Adrenocorticotropic Hormone