Monozygotic twins with congenital adrenal hyperplasia: Long-term endocrine evaluation and gene analysis

Monozygotic female twins with congenital adrenal hyperplasia due to 21-hydroxylase deficiency are described and evaluated over the first 6 years of life. Despite appropriate steroids, NaCl, and fludrocortisone therapies, there was significant fluctuation in the suppression of adrenal steroid secretion. Advanced bone maturation in both was noted. For the first time, molecular genetic analysis was performed and documented that the twins were compound heterozygotes for two different mutations: the maternal allele carried the 8-bp deletion mutation, whereas the paternal allele carried the I172N missense mutation. Parental DNA samples confirmed that the mutations were on different alleles.