Abstract
Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is an autosomal recessive disorder with an incidence of 1:5000 to 1:15000. There are now known to be two 21-hydroxylase genes (21A and 21B) located at the 3' ends of the genes coding for the fourth component of complement (C4) on the short arm of chromosome six. Although the 21A and 21B genes share a high degree of homology and will hybridise to the same DNA probe, they can be distinguished by a number of restriction fragment length polymorphisms.
We have analysed DNA from 30 patients with 21-hydroxylase deficiency - 24 salt losers, 2 non-salt losers and 4 late onset. DNA was isolated from leucocytes, digested with various restriction enzymes and Southern blots prepared. These were hybridised with probes specific for either C4 or the 21-hydroxylase gene. Only two patients were found to have a deletion of the 21B gene on both chromosomes. In one case the adjacent C4B gene was also deleted and appeared to have arisen by recombination between homologous regions of 21A and 21B. 12 other patients were heterozygous for this deletion as judged by the intensity of hybridisation. This finding was not associated with any particular clinical phenotype. A number of cases had no obvious deletion. These may contain only a small change in DNA e.g. a point mutation and are currently being investigated by sequencing of the 21-hydroxylase genes.
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Rumsby, G., Grant, D. DELETION OF THE 21-HYDROXYLASE GENE IN CONGENITAL ADRENAL HYPERPLASIA. Pediatr Res 20, 1200 (1986). https://doi.org/10.1203/00006450-198611000-00159
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DOI: https://doi.org/10.1203/00006450-198611000-00159