A new deletion of the 5 alpha-reductase type 2 gene in a Turkish family with 5 alpha-reductase deficiency

Genetic control of typical and atypical sex development

Sex development relies on the sex-specific action of gene networks to differentiate the bipotential gonads of the growing fetus into testis or ovaries, followed by the differentiation of internal and external genitalia depending on the presence or absence of hormones. Differences in sex development (DSD) arise from congenital alterations during any of these processes, and are classified depending on sex chromosomal constitution as sex chromosome DSD, 46,XY DSD or 46,XX DSD. Understanding the genetics and embryology of typical and atypical sex development is essential for diagnosing, treating and managing DSD. Advances have been made in understanding the genetic causes of DSD over the past 10 years, especially for 46,XY DSD. Additional information is required to better understand ovarian and female development and to identify further genetic causes of 46,XX DSD, besides congenital adrenal hyperplasia. Ongoing research is focused on the discovery of further genes related to typical and atypical sex development and, therefore, on improving diagnosis of DSD.

Validation of steroid ratios for random urine by mass spectrometry to detect 5α-reductase deficiency in Vietnamese children

OBJECTIVES

The 5α-reductase-type-2 deficiency (5ARD2) is a rare autosomal recessive 46,XY disorder of sex development caused by the mutated 5α-reductase type 2 (SRD5A2) gene. In this disease, defective conversion of testosterone to dihydrotestosterone leads to variable presentations of male ambiguous genitalia during fetal development. We aimed to examine characteristics of patients presenting with 5ARD2 over a 4 year period.

METHODS

Random urine samples of control and patients with suspected 5ARD2 were collected and urine steroidomic metabolites were measured by Gas chromatography-mass spectrometry (GC-MS) in the period from 2017 to 2021 at National Children's Hospital, Hanoi Vietnam. 5α- to 5β-reduced steroid metabolite ratio, 5a-tetrahydrocortisol to tetrahydrocortisol (5α-THF/THF), was reviewed by receive operator characteristics (ROC) curve analysis. Molecular testing was offered to 25 patients who were diagnosed with 5ARD2 by GC-MS urinary steroid analysis.

RESULTS

Urine steroidomic profiling was conducted for 104 male controls and 25 patients between the ages of 6 months and 13 years old. Twelve of the twenty-five 5ARD2 patients agreed to undertake genetic analysis, and two mutations of the SRD5A2 gene were detected in each patient, confirming the diagnosis. All patients showed a characteristically low ratio of 5α-THF/THF. There was no overlap of 5α-THF/THF ratio values between control and 5ARD2 groups. The ROC of 5α-THF/THF ratio at 0.19 showed 100% sensitivity and 100% specificity for boys between 6 months and 13 years of age.

CONCLUSIONS

Analysis of the urine steroid metabolome by GC-MS can be used to assist in the diagnosis of 5ARD2. We recommend consideration of random urine steroid analysis as a first-line test in the diagnosis of 5ARD2.

Mutational analysis of SRD5A2: From gene to functional kinetics in individuals with steroid 5α-reductase 2 deficiency

Human steroid 5α-reductase 2 (SRD5A2) plays a determinative role in the masculinization of external genitalia. To date, approximately 114 different mutations of the SRD5A2 gene have been reported; however, little information is available about their impact on catalytic function or their three-dimensional (3D) structures. We determined the effect of point mutations on the testosterone-depend kinetic constants (K_m,app and V_max,app) and structural characteristics of SRD5A2 from Mexican patients with 46,XY-steroid 5α-reductase 2 deficiency. PCR-SSCP assays identified ten distinct gene variants and sequencing analysis identified missense mutations [p.V3I, p.S14R, p.A52T, p.F118L, p.R145W, p.R171S, p.L226P, p.F229S, p.S245Y, and p.A248V]. Mutations were re-created by site-directed mutagenesis and expressed in HEK293 cells. Functional studies demonstrated that 8 variants led to partial (K_m,app = 0.16-2.6 μM; V_max,app = 224-2640 pmol/mg P/min) or complete losses of activity compared to the wild-type enzyme (K_m,app = 0.7 μM; V_max,app = 4044 pmol/mg P/min). All the mutations were assessed using multiple software tools and the results predicted that all of the mutations were associated with disease or damage. Mapping mutations on the model of a 3D structure of SRD5A2 demonstrated alterations in contact sites with their proximal amino acids. Our data show that mutations affect the catalytic efficiency (V_max/K_m) or result in residual enzymatic activity, which could be due to erroneous interactions between amino acid residues, the substrate testosterone, or NADPH.

Genotype-phenotype correlation, gonadal malignancy risk, gender preference, and testosterone/dihydrotestosterone ratio in steroid 5-alpha-reductase type 2 deficiency: a multicenter study from Turkey

BACKGROUND

Studies regarding genetic and clinical characteristics, gender preference, and gonadal malignancy rates for steroid 5-alpha-reductase type 2 deficiency (5α-RD2) are limited and they were conducted on small number of patients.

OBJECTIVE

To present genotype-phenotype correlation, gonadal malignancy risk, gender preference, and diagnostic sensitivity of serum testosterone/dihydrotestosterone (T/DHT) ratio in patients with 5α-RD2.

MATERIALS AND METHODS

Patients with variations in the SRD5A2 gene were included in the study. Demographic characteristics, phenotype, gender assignment, hormonal tests, molecular genetic data, and presence of gonadal malignancy were evaluated.

RESULTS

A total of 85 patients were included in the study. Abnormality of the external genitalia was the most dominant phenotype (92.9%). Gender assignment was male in 58.8% and female in 29.4% of the patients, while it was uncertain for 11.8%. Fourteen patients underwent bilateral gonadectomy, and no gonadal malignancy was detected. The most frequent pathogenic variants were p.Ala65Pro (30.6%), p.Leu55Gln (16.5%), and p.Gly196Ser (15.3%). The p.Ala65Pro and p.Leu55Gln showed more undervirilization than the p.Gly196Ser. The diagnostic sensitivity of stimulated T/DHT ratio was higher than baseline serum T/DHT ratio, even in pubertal patients. The cut-off values yielding the best sensitivity for stimulated T/DHT ratio were ≥ 8.5 for minipuberty, ≥ 10 for prepuberty, and ≥ 17 for puberty.

CONCLUSION

There is no significant genotype-phenotype correlation in 5α-RD2. Gonadal malignancy risk seems to be low. If genetic analysis is not available at the time of diagnosis, stimulated T/DHT ratio can be useful, especially if different cut-off values are utilized in accordance with the pubertal status.

Reprint of "Steroid 5α-reductase 2 deficiency"

Dihydrotestosterone is a potent androgen metabolite formed from testosterone by action of 5α-reductase isoenzymes. Mutations in the type 2 isoenzyme cause a disorder of 46,XY sex development, termed 5α-reductase type 2 deficiency and that was described forty years ago. Many mutations in the encoding gene have been reported in different ethnic groups. In affected 46,XY individuals, female external genitalia are common, but Mullerian ducts regress, and the internal urogenital tract is male. Most affected males are raised as females, but virilization occurs at puberty, and male social sex develops thereafter with high frequency. Fertility can be achieved in some affected males with assisted reproduction techniques, and adults with male social sex report a more satisfactory sex life and quality of life as compared to affected individuals with female social sex.

Steroid 5α-reductase 2 deficiency

Dihydrotestosterone is a potent androgen metabolite formed from testosterone by action of 5α-reductase isoenzymes. Mutations in the type 2 isoenzyme cause a disorder of 46,XY sex development, termed 5α-reductase type 2 deficiency and that was described forty years ago. Many mutations in the encoding gene have been reported in different ethnic groups. In affected 46,XY individuals, female external genitalia are common, but Mullerian ducts regress, and the internal urogenital tract is male. Most affected males are raised as females, but virilization occurs at puberty, and male social sex develops thereafter with high frequency. Fertility can be achieved in some affected males with assisted reproduction techniques, and adults with male social sex report a more satisfactory sex life and quality of life as compared to affected individuals with female social sex.

Phenotype, Sex of Rearing, Gender Re-Assignment, and Response to Medical Treatment in Extended Family Members with a Novel Mutation in the SRD5A2 Gene

Deficiency of steroid 5-alpha reductase-2 (5ARD2) is an inborn error of metabolism causing a disorder of sexual differentiation. It is caused by a mutation in the SRD5A2 gene in which various mutation types have been reported. Affected individuals have a broad spectrum of presentation ranging from normal female-appearing genitalia, cliteromegaly, microphallus, hypospadias, to completely male-appearing genitalia. We report an extended Emirati family with 11 affected members. The family displayed various phenotypes on presentation leading to different sex of rearing. Some family members were reassigned gender at various stages of life. The index case was born with severe undervirilization with bilaterally palpable gonads and was raised as male from birth. He had a 46,XY karyotype and a high testosterone/dihydrotestosterone ratio. Genetic investigation revealed a novel homozygous deletion of exon 2 of the SRD5A2 gene. Both parents were found to be carriers for the gene deletion. The patient had masculinizing surgery and a course of topical dihydrotestosterone. No beneficial effect of the hormone application was noted over 3 months and the treatment was discontinued. The findings on this kindred indicate that deletion of exon 2 in the SRD5A2 gene causes various degrees of genital ambiguity leading to different sex of rearing in affected family members. Gender reassignment may be done at various ages even in conservative communities like the Gulf region.

Ambiguous external genitalia due to defect of 5-α-reductase in seven Iraqi patients: prevalence of a novel mutation

We report on seven Iraqi patients with 46,XY karyotype and ambiguous genitalia characterized by perineo-scrotal hypospadias, bifid scrotum, clitoris like phallus, palpable testes in inguinal canal and pseudovagina. Patients were raised five as females and two as males. They are all unrelated with the exception of two couples of brothers. The diagnosis of 5-α-reductase-2 deficiency syndrome was first hypothesized on clinical grounds and then confirmed by molecular analysis. Direct sequencing analysis of the SRD5A2 gene revealed in five patients a novel homozygous frame-shift mutation (c.453delC) and in two related patients a previous reported missense mutation. The presence of the same mutation in unrelated patients of the same population suggests a possible founder effect. This report brings the 5-α-reductase-2 deficiency syndrome to the attention of clinical geneticists and child surgeons and discusses the appropriate clinical and surgical strategies for treating these patients.

The IVS1-2A>G mutation in the SRD5A2 gene predominates in Cypriot patients with 5α reductase deficiency

BACKGROUND

5α steroid reductase deficiency (5αSRD) is an autosomal recessive enzymatic deficiency and mutations in the 5α steroid reductase type 2 gene (SRD5A2) result in male pseudohermaphrodism caused by decreased dihydrotestosterone (DHT) synthesis.

AIM

To identify the specific mutations of the SRD5A2 gene in Cypriot patients with 5αSRD.

SUBJECTS AND METHODS

Five unrelated patients with 46,XY karyotype were examined. Four of them were born with ambiguous genitalia and 1 patient, who was raised as girl, presented with primary amenorrhea. The hCG test was informative (elevated testosterone/DHT) of 5αSRD in 3 out of 4 subjects. Sequencing of the SRD5A2 gene was completed for all patients. Genomic DNA was also isolated from a total of 204 healthy unrelated Cypriot subjects. Screening for the IVS1-2A>G mutation was performed by using direct sequencing and restriction enzyme analysis.

RESULTS

The IVS1-2A>G was identified in homozygosity in 3 patients and in a compound heterozygote state in the other 2 patients, in combination with p.P181L and p.R171S in exon 3, respectively. The carrier frequency in the Cypriot population for the IVS1-2A>G mutation was estimated to be 0.98% or 2 in 204.

CONCLUSIONS

The same IVS1-2A>G mutation in the SRD5A2 gene seems to characterize all Cypriot patients with 5αSRD diagnosed so far. Furthermore this relatively rare genetic defect, which has only been reported previously in a single case in the Eastern Mediterranean region, is very likely to be the result of a founder effect.

A practical approach to ambiguous genitalia in the newborn period

The evaluation and management of neonates with ambiguous genitalia requires sensitivity, efficiency, and accuracy. The approach to these neonates is facilitated by a multidisciplinary team including urology, endocrinology, genetics, and psychiatry or psychology. Disorders of sex development (DSD) encompass chromosomal DSD, 46,XX DSD, and 46,XY DSD. The 46,XX DSD is the most common DSD and in the majority of these children congenital adrenal hyperplasia is the underlying etiology. The 46,XY DSD is a heterogeneous disorder that often results from a disruption in the production or response to testosterone, dihydrotestosterone, or Mullerian inhibitory substance. Chromosomal DSD includes conditions resulting from abnormal meiosis, including Klinefelter syndrome (47, XXY) and Turner syndrome. The evaluation of children with DSD demands a thorough physical examination, medical history, karyotype, metabolic panel, 17-OH progesterone, testosterone, luteinizing hormone, follicle stimulation hormone, and urinalysis. A radiographic evaluation should begin with an abdominal and pelvic ultrasound but may include magnetic resonance imaging, endoscopy, or laparoscopy.

Hormonal abnormalities leading to disorders of sexual development

Normal human sexual development occurs in a highly regulated process that comprises three distinct phases: establishment of chromosomal sex, development of the sex-specific gonads and phenotypic differentiation of the internal ductal anatomy and external genitalia. The latter two phases are mediated by specific hormonal effector molecules, including anti-Müllerian hormone and testosterone, and their dysregulation often leads to the development of a phenotypic disorder of sexual differentiation. This review describes the hormonal mediators that are involved in sexual development and the disorders of sexual differentiation that arise from their dysfunction.

A novel missense mutation of 5-alpha reductase type 2 gene (SRD5A2) leads to severe male pseudohermaphroditism in a Turkish family

OBJECTIVES

To analyze the steroid 5-alpha reductase type 2 gene (SRD5A2) in 2 siblings with severe male pseudohermaphroditism suspected to have 5-alpha reductase deficiency in a Turkish family.

METHODS

Two female siblings of a family with 7 children were referred to the urology department because of bilateral inguinal masses. The patients had presented after birth with ambiguous genitalia, but no further diagnostic procedures had been performed, and they were raised as girls until the ages of 13 and 15 years. At this time, both had striking ambiguity of the genitalia, with a clitoris-like phallus, severely bifid scrotum, pseudovaginal perineoscrotal hypospadias, a rudimentary prostate, and inguinal testes. Karyotype was 46,XY. Basal and stimulated levels of serum testosterone (T), dihydrotestosterone (DHT), and T/DHT ratio indicated 5-alpha reductase deficiency. Molecular genetic analysis was performed on deoxyribonucleic acid from peripheral blood leukocytes by single-stranded conformational polymorphism analysis and direct sequencing.

RESULTS

Analysis of the SRD5A2 gene revealed a new homozygous missense mutation in exon 2. At codon 123, we identified a GGA to AGA change resulting in a missense amino acid change from glycine to arginine (G123R). Both parents and the 2 healthy sisters and 3 brothers were all heterozygous at codon 123 for the same mutation.

CONCLUSIONS

We report a novel homozygous missense mutation in exon 2 of the 5-alpha reductase type 2 gene that led to severe undervirilization in 2 siblings.

Clinical, Biochemical and Morphologic Diagnostic Markers in an Infant Male Pseudohermaphrodite Patient with Compound Heterozygous Mutations (G115D/R246W) in SRD5A2 Gene

A patient with male pseudohermaphroditism and clinical diagnosis of partial androgen insensitivity in the neonatal period was studied at pubertal age for a molecular diagnosis. Hormone studies were conducted at baseline and under hCG stimulation for testosterone and dihydrotestosterone determinations at 2 months of age. Gonadectomy was performed at 4 months. At the age of 13 years genital skin fibroblasts were studied for androgen binding and 5alpha-reductase activity and peripheral blood DNA was available for androgen receptor (AR) and 5alpha-reductase (SRD5A2) gene analysis. Exons 1-8 of AR gene and exons 1-5 of SRD5A2 gene were sequenced. AR gene coding sequences were normal. SRD5A2 gene analysis revealed two heterozygote mutations (G115D and R246W), with the mother carrying the G115D and the father the R246W mutations. The compound heterozygote mutations in SRD5A2 gene explained an extremely low 5alpha-reductase enzyme activity in genital skin fibroblasts. Revision of hormonal data from the neonatal period revealed an increased testosterone-to-dihydrotestosterone ratio at the end of an hCG stimulation test, which concurred with the molecular diagnosis. Testis morphology at 4 months of age was normal. Clinical and biochemical differential diagnosis between partial androgen insensitivity syndrome and 5alpha-reductase enzyme deficiency is difficult in the neonatal period and before puberty. Our results show that in our patient the testosterone-to-dihydrotestosterone ratio would have adequately orientated the diagnosis. The two mutations in SRD5A2 gene have been described in patients of different lineages, though not in combination to date. Testis morphology showed that, during early infancy, the 5alpha-reductase deficiency may not have affected interstitial or tubular development.

A practical approach to intersex in the newborn period

Sexual determination is a complex process that occurs in an organized sequential manner. When chromosomal, gonadal, or phenotypic sex determination goes awry,intersexuality develops. Advances in molecular biology have made it easier to understand the various phenotypes that are encountered. It is easy to be overwhelmed when reviewing the testosterone synthesis pathway and the intersex differential diagnosis. This article presents a useful approach to the evaluation of the newborn with ambiguous genitalia.

Compound heterozygous mutations in the SRD5A2 gene exon 4 in a male pseudohermaphrodite patient of Chinese origin

The goal of this study was to perform 5-alpha-reductase type 2 gene (SRD5A2) analysis in a male pseudohermaphrodite (MPH) patient with normal testosterone (T) production and normal androgen receptor (AR) gene coding sequences. A patient of Chinese origin with ambiguous genitalia at 14 months, a 46,XY karyotype, and normal T secretion under human chorionic gonadotropin (hCG) stimulation underwent a gonadectomy at 20 months. Exons 1-8 of the AR gene and exons 1-5 of the SRD5A2 gene were sequenced from peripheral blood DNA. AR gene coding sequences were normal. SRD5A2 gene analysis revealed 2 consecutive mutations in exon 4, each located in a different allele: 1) a T nucleotide deletion, which predicts a frameshift mutation from codon 219, and 2) a missense mutation at codon 227, where the substitution of guanine (CGA) by adenine (CAA) predicts a glutamine replacement of arginine (R227Q). Testes located in the inguinal canal showed a normal morphology for age. The patient was a compound heterozygote for SRD5A2 mutations, carrying 2 mutations in exon 4. The patient showed an R227Q mutation that has been described in an Asian population and MPH patients, along with a novel frameshift mutation, Tdel219. Testis morphology showed that, during early infancy, the 5-alpha-reductase enzyme deficiency may not have affected interstitial or tubular development.

Mutations of the 5alpha-steroid reductase type 2 gene in six Turkish patients from unrelated families and a large pedigree of an isolated Turkish village

We describe six Turkish patients with 5alpha-steroid reductase type 2 deficiency from unrelated Turkish families and a large pedigree of one of these patients who reside north-west of Anatolia. Patients NA, KS, BD and SY presented for evaluation of bilateral inguinal masses with female phenotypes. Patient ABE had penoscrotal hypospadias with male phenotype. Homozygous mutation of the 5alphaSR2 gene was identified in five of these patients by genomic DNA analysis. These mutations were Leu55Gln in exon 1 (in patients FG, BD and ABE), deltaMet157 in exon 3 (in patient NA), and splice junction abnormality in intron 1 (in patient SY). One individual (patient KS) was found to be a compound heterozygous carrier of two different mutations, Leu55Gln in exon 1 and Arg171Ser in exon 3. Patient FG had a large pedigree with the Leu55Gln mutation in exon 1. The pedigree of this family with marital consanguinity is remarkable, and possibly due to the isolation of this family because of economic and social problems. A further 85 individuals belonging to this family were analyzed for exon 1 Leu55Gln mutations in the 5alphaSR2 gene. Forty-two of these 85 individuals (49.41%) had this alteration; 11 were homozygous (8 genetic male, 3 genetic female) and 31 heterozygous (18 genetic male, genetic female) for this mutation. It was interesting to see asymptomatic homozygous female carriers. In conclusion, according to our results and those of other Turkish patients reported by different investigators, 5aSR2 gene mutation analysis, especially for Leu55Gln in exon 1 and deltaMet157 in exon 3, must be carried out in Turkish patients with male pseudohermaphroditism. Homozygous asymptomatic female carriers must be taken into consideration in this clinical entity, especially in a closed population, because of the risk of transmitting the disease to their offspring.

Identification of missense mutations in the SRD5A2 gene from patients with steroid 5alpha-reductase 2 deficiency

BACKGROUND AND OBJECTIVE

Mutations of the steroid 5alpha-reductase type 2 (SRD5A2) gene in karyotypic males result in a spectrum of external genitalia phenotypes ranging from complete female to nearly complete male. Here we performed genomic DNA analyses from individuals bearing the enzyme deficiency in order to detect the molecular abnormalities.

PATIENTS

Four unrelated 46,XY patients of Mexican origin with ambiguous external genitalia were studied. A fertile, phenotypically normal male was also included.

MEASUREMENTS

Coding sequence abnormalities of the SRD5A2 gene were assessed by exon-specific polymerase chain reaction, single-stranded conformational polymorphism and sequencing analysis.

RESULTS

Five different missense mutations (two of them novel mutations) were identified. Three subjects presented homozygous single base mutations. These were located at exon 2 (G115D), exon 4 (P212R) and exon 5 (R246Q), and such changes have been described previously. The fourth patient was a compound heterozygote who presented two mutations located in exons 1 and 2. We found a hitherto unreported G --> A transition at the second nucleotide of codon 85 in exon 1 (GGC --> GAC), substituting glycine for aspartic acid (G85D). This patient also presented an identical alteration at codon 115 of exon 2, which was carried by his father (G115D). Finally, in another subject who was included originally as a control, we found a C --> A transversion (yet undescribed) at codon 245 in exon 5 (S245Y).

CONCLUSIONS

Four different single base mutations that cause amino acid substitutions were detected in the steroid 5alpha-reductase type 2 gene of affected individuals. One patient and a normal control had two previously undescribed mutations. Although in the latter individual we cannot exclude the possibility that the base change is a genetic polymorphism, the molecular screening of 100 chromosomes suggests strongly that the change at codon 245 does represent a heterozygous mutation. Further studies, including the recreation of the mutations, will help to reveal the biochemical consequences resulting from these changes.

New frameshift mutation in the 5alpha-reductase type 2 gene in a Brazilian patient with 5alpha-reductase deficiency

Male pseudohermaphroditism caused by steroid 5alpha-reductase deficiency is an autosomal recessive disorder. The enzyme steroid 5alpha-reductase 2 (encoded by the SRD5A2 gene) catalyses the conversion of testosterone to dihydrotestosterone, which is required for normal differentiation of the external male genitalia. This report describes the molecular analysis of the 5alpha-reductase type 2 gene in a Brazilian patient who was raised as a female, underwent a reversal of gender role behavior, and is now a married man. This patient is a compound heterozygote bearing an A-->G mutation within exon 2, changing codon 126 from Glu to Arg on one allele and a novel single base deletion (418delT) causing a frameshift mutation at codon 140 in the same exon, on the other allele. This last mutation probably leads to the synthesis of a truncated protein, because a premature termination signal is created at codon 159.

Molecular characterization of 5 alpha-reductase type 2 deficiency and fertility in a Swedish family

The molecular background of 5 alpha-reductase type 2 deficiency was investigated in a Swedish family with no known consanguinity and in which the affected males were fertile. The three male siblings were born with ambiguous external genitalia, and the diagnosis of 5 alpha-reductase deficiency was established at the ages of 16, 14, and 10 yr, respectively. All three siblings underwent surgery for hypospadias repair. At least two of the brothers are demonstrably fertile. Molecular analysis showed the three brothers to be compound heterozygotes, carrying two different mutations in exon 4 of the 5 alpha-reductase type 2 gene. The two mutations (G196S and H231R) have been described previously and reported to give rise to partially functioning enzymes, which may explain the milder phenotype and perhaps the fertility in the preset three patients.

The identification of 5 alpha-reductase-2 and 17 beta-hydroxysteroid dehydrogenase-3 gene defects in male pseudohermaphrodites from a Turkish kindred

Male pseudohermaphroditism (MPH) is characterized by incomplete differentiation of male genitalia in the presence of testicular tissue. Enzymatic defects involving androgen synthesis or action are causes of MPH. We studied the molecular genetics of a large isolated inbred Turkish kindred with MPH due to either 5 alpha-reductase-2 (SRD5A2) or 17 beta-hydroxysteroid dehydrogenase-3 (17 beta HSD3) gene defects. Using single strand DNA conformational polymorphism analysis and DNA sequencing, a new mutation in exon 5 of SRD5A2 gene was detected in certain male pseudohermaphrodites from this kindred. This single base deletion (adenine) resulted in a frame shift at amino acid position 251 resulting in the addition of 23 amino acids at the carboxyl-terminal of this 254-amino acid isozyme. Transfection expression of the mutant isozyme in CV1 cells showed a complete loss of enzymatic activity in the conversion of [14C]testosterone to dihydrotestosterone, without a change in the messenger ribonucleic acid level compared to that of the wild-type isozyme. Analysis of the 17 beta HSD3 gene in other male pseudohermaphrodites from this kindred revealed a single point mutation (G-->A) at the boundary between intron 8 and exon 9, disrupting the splice acceptor site of exon 9. In this kindred, in addition to the identification of male pseudohermaphrodites with either a homozygous SRD5A2 or 17 beta HSD3 gene defect, other male pseudohermaphrodites were found to be genetically more complex: e.g. homozygous for the SRD5A2 defect and heterozygous for the 17 beta HSD3 defect, or homozygous for the 17 beta HSD3 defect and heterozygous for the SRD5A2 defect. Also, phenotypically normal carriers were identified with either one or both gene defects. Homozygous male pseudohermaphrodites with SRD5A2 or 17 beta HSD3 gene defects were phenotypically distinguishable by the presence of mild gynecomastia in the latter. Hormone data were consistent with the particular homozygous gene defect. In summary, we show 1) the novel existence of two gene defects, SRD5A2 and 17 beta HSD3, each causing MPH within a large isolated Turkish kindred; 2) that the two defects segregate independently and may be inherited from two different progenitors; and 3) analysis of a new mutation in exon 5 of SRD5A2 gene, supporting the functional importance of the carboxyl-terminal of 5 alpha-reductase-2 isozyme.

Diagnosis of 5alpha-reductase deficiency in a teenage Turkish girl

Deficiency of 5alpha-reductase type 2 activity causes deficient masculinization of 46,XY individuals caused by a lack of dihydrotestosterone. At puberty, virilization is often observed. A precise diagnosis with correct gender assignment at an early age is very important. Recently, the molecular basis of the enzyme defect was discovered; however, only a few cases of 5alpha-reductase deficiency with a complete molecular genetic analysis have been published. We report on a Turkish patient clinically classified with steroid 5alpha-reductase deficiency (SRD) type 3b (karyotype 46,XY) who was raised as a girl and presented to us at the age of 14 years because the male phenotype had become predominant at puberty. Endocrinological investigations revealed an elevated serum testosterone/dihydrotestosterone ratio (17.3, normal: <16). PCR-SSCP analyses detected a deletion of methionine on exon 3 of the 5alpha-reductase type 2 gene.