Molecular genetics and phenotype/genotype correlation of 5-α reductase deficiency in a highly consanguineous population.

CONTEXT AND OBJECTIVES: 5-α reductase deficiency is a rare 46,XY disorder of sex development. We present detailed phenotypic and genotypic features of a cohort of 24 subjects from a highly consanguineous population of Saudi Arabia SUBJECTS AND METHODS: We studied the clinical presentation and hormonal profiles of 24 subjects diagnosed with 5-α reductase deficiency and performed genetic testing on DNA isolated from their peripheral blood using polymerase chain reaction and direct sequencing of the SRD5A2. RESULTS: All subjects had 46,XY karyotype and presented with atypical appearance of external genitalia ranging from clitoromegaly, micophallus with hypospadias, undescended testes to completely normally looking female genitalia. Thirteen (54%) of them had severe under virilization and were assigned female sex at birth. The other 11 subjects were raised as males. Stimulated Testosterone:Dihydrotestosterone ratio was high in all 16 subjects in whom it was measured. The genetic testing revealed 2 nonsense mutations (p.R103X and p.R227X) in 2 unrelated subjects, 3 missense mutations (p.P181L, p.A228T, p.R246Q) in 11 subjects and a splice site mutation (IVS1-2A > G) in 11 other subjects. There was significant phenotypic variability even in subjects with the same mutation and also within the same family. CONCLUSION: This is the first and largest report of the clinical and molecular genetics of 5-α reductase deficiency from the Middle East. It shows weak genotype/phenotype correlation and significant phenotypic heterogeneity. IVS1-2A > G mutation is the most common mutation and is likely to be a founder mutation in this part of the world.

Mutational analysis of rare subtypes of congenital adrenal hyperplasia in a highly inbred population.

CONTEXT: Apart from 21 Hydroxylase deficiency, other subtypes of congenital adrenal hyperplasia (CAH) are rare. We studied the clinical features and molecular genetics of a relatively large series of patients with CYP17A1, HSD3ß2 and StAR deficiencies. PATIENTS AND METHODS: We studied 21 patients including 7 patients with CYP17A1, 10 patients with HSD3ß2 and 4 patients with StAR deficiencies. For mutation detection, we isolated DNA from peripheral leucocytes, amplified genes of interest using polymerase chain reaction and directly sequenced the amplicons using Dideoxy Chain Termination method. RESULTS: Regardless of their karyotype, patients with CYP17A1 deficiency presented with normally looking external female genitalia and were raised as females. Hypertension and hypokalemia were prominent features in 4 of 7 patients. Two missense (p.R416H, p.R239Q) and 2 non-sense (p.Y329X, p.Y329X) mutations were found in these 7 cases. In 3 unrelated families with 10 affected siblings with HSD3ß2 mutations, two non-sense mutations were found (p.Q334X, p.R335X). 46XY patients with HSD3ß2 deficiency presented with ambiguous genitalia while 46XX patients presented with normal female external genitalia. Adrenal crisis was common in patients with both karyotypes. In the 4 patients with StAR deficiency, both genetic male and female patients presented with normally looking female external genitalia and adrenal crisis. One previously reported missense mutation (p.R182H) was found in 3 unrelated patients and a novel non-sense mutation (p.Q264X) in the fourth patient. CONCLUSIONS: These cases of rare subtypes of CAH illustrate the heterogeneous phenotypic and genetic features of these subtypes and add unique novel mutations to the previously known ones.

A high rate of novel CYP11B1 mutations in Saudi Arabia.

Despite ethnic variation, 11 ß-hydroxylase deficiency (11ß-OHD) has generally been considered the second most common subtype of congenital adrenal hyperplasia (CAH). We report a high rate of novel mutations in this gene (CYP11B1) in patients from Saudi Arabia. We studied 16 patients with 11ß-OHD from 8 unrelated families. DNA was isolated from peripheral blood. The 9 exons and exon-intron boundaries of CYP11B1 were PCR-amplified and directly sequenced. The novel mutations were functionally characterized using subcloning, in vitro mutagenesis, cell transfection and 11-deoxycortisol: cortisol conversion assays. Six mutations were found in these 8 unrelated families. Three of these mutations are completely novel and two have just been recently described as novel mutations from the same population. These include a single nucleotide insertion mutation in codon 18 (c.53_54insT) leading to frameshift and truncation in 4 siblings, a novel mutation (c.1343G>C, p.R448P) in 3 unrelated families, a novel mutation (c.1394A>T, p.H465L) in 2 siblings, a novel mutation (c.617G>T, p.G206V) in 1 patient, and a recently described non-sense novel mutation (c.780G>A, p.W260X) in another patient. Out of the 6 mutations described in this report, only one mutation (p.Q356X) was reported previously. In vitro functional testing of the 3 missense and nonsense novel mutations revealed complete loss of the 11 hydroxylase activity. We conclude that 11 ß-OHD in Saudi Arabia has a unique genotype with a high rate of novel mutations. The novel p. R448P mutation is the most common mutation in this highly inbred population.