Impact of Estrogen Replacement Therapy in a Male with Congenital Aromatase Deficiency Caused by a Novel Mutation in the CYP19 Gene

Recent reports of the impact of estrogen receptor and aromatase deficiency have shed new light on the importance of estrogen for bone formation in man. We describe a novel mutation of the CYP19 gene in a 27-yr-old homozygous male of consanguinous parents .ACt o Asubstitution in intron V, at position 3 of the splicing acceptor site before exon VI of the CYP19 gene, is the likely cause of loss of aromatase activity. The mRNA of the patient leads to a frameshift and a premature stop codon 8 nucleotides downstream the end of exon V. Both parents were shown to be heterozygous for the same mutation. Apart from genua valga, kyphoscoliosis, and pectus carniatus, the physical examination was normal including secondary male characteristics with normal testicular size. To substitute for the deficiency, the patient was treated with 50 g transdermal estradiol twice weekly for 3 months, followed by 25 g twice weekly. After 6 months estrogen levels (<20 at baseline and 45 pg/ml at 6 months; normal range, 10 –50) and estrone levels (17 and 34 ng/ml; normal range, 30 – 85) had normalized. Bone maturation progressed and the initially unfused carpal and phalangeal epiphyses began to close within 3 months and were almost completely closed after 6 months. The bone age, assessed by roentgenographic standards for bone development by Gruelich and Pyle, was 16.5 at baseline and 18 –18.5 yr after 6 months of treatment. Bone density of the distal radius (left), assessed by quantitative computed tomog