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

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.

The Molecular Basis of 5α-Reductase Type 2 Deficiency

The 5α-reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, playing a crucial role in male development. This enzyme is encoded by the SRD5A2 gene, which maps to chromosome 2 (2p23), consists of 5 exons and 4 introns, and encodes a 254 amino acid protein. Disruptions in this gene are the molecular etiology of a subgroup of differences of sex development (DSD) in 46,XY patients. Affected individuals present a large range of external genitalia undervirilization, ranging from almost typically female external genitalia to predominantly typically male external genitalia with minimal undervirilization, including isolated micropenis. This is an updated review of the implication of the SRD5A2 gene in 5α-reductase type 2 enzyme deficiency. For that, we identified 451 cases from 48 countries of this particular 46,XY DSD from the literature with reported variants in the SRD5A2 gene. Herein, we present the SRD5A2 mutational profile, the SRD5A2 polymorphisms, and the functional studies related to SRD5A2 variants to detail the molecular etiology of this condition.

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.

Integrative and Analytical Review of the 5-Alpha-Reductase Type 2 Deficiency Worldwide

Introduction

The conversion of testosterone into dihydrotestosterone is catalyzed by the 5α-reductase type 2 enzyme which plays a crucial role in the external genitalia virilization. It is encoded by the SRD5A2 gene. Allelic variants in this gene cause a 46,XY DSD with no genotype-phenotype relationship. It was firstly reported in the early 70s from isolated clusters. Since then, several cases have been reported. Putting together, it will expand the knowledge on the molecular bases of androgen milieu.

Methods

We searched for SRD5A2 allelic variants (AV) in the literature (PubMed, Embase, MEDLINE) and websites (ensembl, HGMD, ClinVar). Only cases with AV in both alleles, either in homozygous or compound heterozygous were included. The included cases were analyzed according to ethnicity, exon, domain, aminoacid (aa) conservation, age at diagnosis, sex assignment, gender reassignment, external genitalia virilization and functional studies. External genitalia virilization was scored using Sinnecker scale. Conservation analysis was carried out using the CONSURF platform. For categorical variables, we used X2 test and Cramer's V. Continuous variables were analyzed by t test or ANOVA. Concordance was estimated by Kappa.

Results

We identified 434 cases of 5ARD2 deficiencies from 44 countries. Most came from Turkey (23%), China (17%), Italy (9%), and Brazil (7%). Sixty-nine percent were assigned as female. There were 70% of homozygous allelic variants and 30% compound heterozygous. Most were missense variants (76%). However, small indels (11%), splicing (5%) and large deletions (4%) were all reported. They were distributed along with all exons with exon 1 (33%) and exon 4 (25%) predominance. Allelic variants in the exon 4 (NADPH-binding domain) resulted in lower virilization (p<0.0001). The codons 55, 65, 196, 235 and 246 are hotspots making up 25% of all allelic variants. Most of them (76%) were located at conserved aa. However, allelic variants at non-conserved aa were more frequently indels (28% vs 6%; p<0.01). The overall rate of gender change from female to male ranged from 16% to 70%. The lowest rate of gender change from female to male occurred in Turkey and the highest in Brazil. External genitalia virilization was similar between those who changed and those who kept their assigned gender. The gender change rate was significantly different across the countries (V=0.44; p<0.001) even with similar virilization scores.

Conclusion

5ARD2 deficiency has a worldwide distribution. Allelic variants at the NADPH-ligand region cause lower virilization. Genitalia virilization influenced sex assignment but not gender change which was influenced by cultural aspects across the countries. Molecular diagnosis influenced on sex assignment, favoring male sex assignment in newborns with 5α-reductase type 2 deficiency.

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.

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.

Molecular genetics of hypospadias and cryptorchidism recent developments

During the last decade, a tremendous amount of work has been devoted to the study of the molecular genetics of isolated hypospadias and cryptorchidism, two minor forms of disorders of sex development (DSD). Beyond the genes involved in gonadal determination and sex differentiation, including those underlying androgen biosynthesis and signaling, new genes have been identified through genome-wide association study and familial clustering. Even if no single genetic defect can explain the whole spectrum of DSD, these recent studies reinforce the strong role of the genetic background in the occurrence of these defects. The timing of signaling disruption may explain the different phenotypes.

5-α-Reductase type 2 deficiency: is there a genotype-phenotype correlation? A review

5-α-Reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, a potent androgen responsible for male sexual development during the fetal period and later during puberty. Its deficiency causes an autosomal recessive disorder of sex development characterized by a wide range of under-virilization of external genitalia in patients with a 46,XY karyotype. Mutations in the SRD5A2 gene cause 5-α-Reductase deficiency; although it is an infrequent disorder, it has been reported worldwide, with mutational heterogeneity. Furthermore, it has been proposed that there is no genotype-phenotype correlation, even in patients carrying the same mutation. The aim of this review was to perform an extensive search in various databases and to select those articles with a comprehensive genotype and phenotype description of the patients, classifying their phenotypes using the external masculinization score (EMS). Thus, it was possible to objectively compare the eventual genotype-phenotype correlation between them. The analysis showed that for most of the studied mutations no correlation can be established, although the specific location of the mutation in the protein has an effect on the severity of the phenotype. Nevertheless, even in patients carrying the same homozygous mutation, a variable phenotype was observed, suggesting that additional genetic factors might be influencing it. Due to the clinical variability of the disorder, an accurate diagnosis and adequate medical management might be difficult to carry out, as is highlighted in the review.

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, genotype and gender identity in a large cohort of patients from India with 5α-reductase 2 deficiency

Deficiency of the 5α-reductase 2 enzyme impairs the conversion of testosterone to dihydrotestosterone (DHT) and differentiation of external genitalia, seminal vesicles and prostate in males. The present study describes the phenotype, genotype and gender identity in a large cohort of patients with 5αRD2. All patients underwent detailed clinical evaluation, hormonal profile, karyotyping and molecular analysis of the SRD5A2 gene. The molecular analysis of the SRD5A2 gene showed the presence of mutant alleles in 24 patients. We found 6 novel mutations IVS(1-2) T>C, p.A52T, 188-189insTA, 904-905ins A, p.A12T and p.E57X in our patients. All patients had ambiguous genitalia and the degrees of under-virilization ranged from penoscrotal hypospadias and microphallus to clitoromegaly. The position of gonads was variable in patients with same mutation. All the patients with mutations in the SRD5A2 gene had male gender identity. Those reared as female had gender dysphoria and underwent gender reassignment. Though a specific genotype-phenotype correlation could not be established in our patient but confirming the diagnosis of 5αRD2 with assessment of the SRD5A2 gene may help in appropriate gender assignment.

Phenotype and molecular characteristics in 45 Chinese children with 5α-reductase type 2 deficiency from South China

CONTEXT

Affected by steroid 5α-reductase type 2 deficiency (5α-RD2), 46, XY individuals present divergent phenotypes characterized by undervirilization of male external genitalia. To identify the disorder, mutational analysis of 5α-reductase type 2 gene (SRD5A2) is a reliable approach. The genotype-phenotype relationship has not been elucidated.

OBJECTIVE

To improve the diagnosis and expand the knowledge of the disease, we collected and analysed relevant data of clinical diagnosis, biological investigation and molecular determination in 45 children with the SRD5A2 gene mutations from South China in our centre.

SUBJECTS AND METHODS

We studied a cohort of 45 Chinese children with SRD5A2 gene mutations.

RESULTS

Isolated microphallus (35·6%) and microphallus associated with various degrees of hypospadias (55·6%) were frequent phenotype. Female external genitalia with clitoromegaly (8·9%) were rare. 16 of 18 (88·9%) cases had hCG-stimulated T/DHT ratio above 10. In 45 patients, we identified 15 different mutations. Five have never been described: p.His90ThrfsX31, p.Gly21Arg, p.Gly149Asp, p.Arg145Leu and p.Gly66Arg. The p.Arg227Gln mutation was detected in 41 (91·1%) patients. The p.Leu89Val polymorphism was found in 38 (84·4%) patients. Homozygous mutations were presented in 16 (35·6%) patients, compound heterozygous mutations in 20 (44·4%) patients, compound heterozygous mutations alone with the p.Leu89Val polymorphism in nine (20·0%) patients. Exons 1 and 4 were most affected, and the number of mutant alleles per exon was 78·1% and 12·2%, respectively.

CONCLUSIONS

The study demonstrated a wide spectrum of phenotypes, biological profiles and genotypes in the children with 5α-RD2 from South China. The heterozygous mutation p.Arg227Gln is presumably a hot spot mutation and suggests a founder effect in the population of South China that may explain a moderate phenotype among our patients. Our report provides new insights into the molecular mechanism of 5α-RD2 and help to the diagnosis and treatment of this disease.

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.

Novel mutation of SRD5A2 gene in a patient with 5α-reductase 2 deficiency from India

Master N had genital malformation at birth and had bilateral gonads in the labial fold. He was reared as a boy and corrective surgery was done at the age of 4&emsp14;years and was reassessed at the age of 14&emsp14;years. His testosterone/dihydrotestosterone (DHT) was 11.8 (reference range <=10). Molecular analysis of SRD5A2 gene indicated the presence of a novel heterozygous missense mutation of p.A52T in exon 1, which was also detected in mother. The father, sister and maternal grandfather were found to have normal SRD5A2 gene sequence. We also detected an intronic (1-2) homozygous T>C transition in patient, whereas both parents were found to have the same transition in heterozygous form. Although 5α-steroid reductase 2 deficiency is an autosomal-recessive disorder, in this case, it appears that there may be a dominant inheritance because only one identified mutation was present which was passed from mother to son.

Current concepts in disorders of sexual development

Disorders of sex development (DSD) with or without ambiguous genitalia require medical attention to reach a definite diagnosis. Advances in identification of molecular causes of abnormal sex, heightened awareness of ethical issues and this necessitated a re-evaluation of nomenclature. The term DSD was proposed for congenital conditions in which chromosomal, gonadal or anatomical sex is atypical. In general, factors influencing sex determination are transcriptional regulators, whereas factors important for sex differentiation are secreted hormones and their receptors. The current intense debate on the management of patients with intersexuality and related conditions focus on four major issues: 1) aetiological diagnosis, 2) assignment of gender, 3) indication for and timing of genital surgery, 4) the disclosure of medical information to the patient and his/her parents. The psychological and social implications of gender assignment require a multidisciplinary approach and a team which includes ageneticist, neonatologist, endocrinologist, gynaecologist, psychiatrist, surgeon and a social worker. Each patient should be evaluated individually by multidisciplinary approach.

Hypospadias: interactions between environment and genetics

Hypospadias is one of the most common congenital malformations. It is considered to be a mild form of the 46,XY disorders of sex development (DSD), but its precise etiology remains to be elucidated. Compromised androgen synthesis or effects can cause this frequent malformation, although the mutational analyses of the genes involved in androgen actions have identified abnormalities in only a very small portion of patients. The overwhelming majority of cases remain unexplained and hypospadias may be a highly heterogeneous condition subject to multiple genetic and environmental factors. We here review the recent advances in this field and discuss the potential interactions between the environment and genetics.

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.

Disorders of sexual development: an overview of 18 years experience in the pediatric Endocrinology Department of Ankara University

INTRODUCTION

Disorders of sexual development (DSD) occur when the appearance of the internal and/or external genitalia is at variance with normal development for either sex. We reviewed the characteristics of patients with DSD.

PATIENTS

Two hundred and eight children aged from newborn to 19 years with DSD from 1990 to 2008.

RESULTS

46,XY DSD (52.4%) was more common than 46,XX DSD (34.6%) and gonadal differentiation disorders (12.99%). Thirty-six (33.02%) patients were diagnosed with androgen resistance syndrome, 41 (37.61%) had 5alpha-reductase deficiency, 23 (21.10%) had testosterone synthesis disorders. Congenital adrenal hyperplasia was the most frequent underlying cause of 46,XX DSD.

CONCLUSION

There are many difficult aspects in the diagnosis and management of DSD. Gender assessment teams of endocrine centers need a multidisciplinary approach for the diagnosis, medical and surgical treatment, genetic counseling, and psychosocial support of these patients.

A novel mutation of 5alpha-steroid reductase 2 deficiency (CD 65 ALA-PRO) with severe virilization defect in a Turkish family and difficulty in gender assignment

Molecular genetic characterization of mutations in SRD5A2 gene is used as an essential procedure for the final diagnosis of 5alpha-reductase deficiency. Here, we report a novel homozygous point mutation of SRD5A2 gene at codon 65 in exon 1, due to a proline for alanine substitution in a Turkish family whose proband has severe undervirilization. This mutation has not been reported up to date in association with 5alpha-reductase deficiency in various ethnic groups. We discussed some questions about gender assignment in addition to the molecular and clinical characteristics of the disease.

Genetic analysis of the SRD5A2 gene in Indian patients with 5alpha-reductase deficiency

BACKGROUND

5alpha-Reductase deficiency (5RD) is an uncommon autosomal recessive disorder of sexual differentiation. It results from impaired conversion of testosterone to dihydrotestosterone due to mutations in the steroid 5alpha-reductase type 2 gene (SRD5A2). Mutations in SRD5A2 have not been previously reported in Indian patients with 5RD.

AIM

To delineate the clinical features and mutations in the SRD5A2 gene in Indian patients with 5RD.

PATIENTS AND METHODS

The SRDSA2 gene was sequenced in two unrelated patients with elevated testosterone/dihydrotestosterone ratio and in one patient with classical clinical features and virilization at puberty (in whom the ratio could not be measured due to prior gonadectomy). The prevalence of SRD5A2 mutations was also studied in 52 healthy ethnic control subjects by PCR-RFLP.

RESULTS

Two patients, both from the north Indian state of Uttar Pradesh, carried the homozygous missense mutation p.R246Q in exon 5. Parents of both probands were heterozygous for the mutation. The mutation was absent in 52 control subjects. The third patient, with severe perineoscrotal hypospadias and micropenis, was detected to have a novel heterozygous missense mutation p.Q56H, as well as the homozygous polymorphism p.V89L, both in exon 1. The p.Q56H mutation was absent in 52 control subjects.

CONCLUSION

p.R246Q is a common SRD5A2 mutation in 5RD patients from the Indian subcontinent.

Is hypospadias a genetic, endocrine or environmental disease, or still an unexplained malformation?

Hypospadias is one of the most frequent genital malformations in the male newborn and results from an abnormal penile and urethral development. This process requires a correct genetic programme, time- and space-adapted cellular differentiation, complex tissue interactions, and hormonal mediation through enzymatic activities and hormonal transduction signals. Any disturbance in these regulations may induce a defect in the virilization of the external genitalia and hypospadias. This malformation thus appears to be at the crossroads of various mechanisms implicating genetic and environmental factors. The genes of penile development (HOX, FGF, Shh) and testicular determination (WT1, SRY) and those regulating the synthesis [luteinizing hormone (LH) receptor] and action of androgen (5alpha reductase, androgen receptor) can cause hypospadias if altered. Several chromosomal abnormalities and malformative syndromes include hypospadias, from anterior to penoscrotal forms. More recently, CXorf6 and ATF3 have been reported to be involved. Besides these genomic and hormonal factors, multiple substances found in the environment can also potentially interfere with male genital development because of their similarity to hormones. The proportion of hypospadias cases for which an aetiology is detected varies with the authors but it nevertheless remains low, especially for less severe cases. An interaction between genetic background and environment is likely.

[5alpha-reductase type 2 deficiency: experiences from Campinas (SP) and Salvador (BA)]

OBJECTIVE

To report the experience regarding patients with steroid 5alpha-reductase type 2 deficiency from three different clinical services in Brazil.

CASUISTIC AND METHODS

Twenty five patients with clinical and hormonal features of 5alpha-reductase deficiency from 23 families (15 from Bahia, 7 from São Paulo and 1 from Minas Gerais) were included in this study. Clinical, hormonal and molecular data were evaluated. The molecular analysis of the five exons of the SRD5A2 gene was done by automatic or manual sequencing of PCR products.

RESULTS

In ten families, SRD5A2 mutations were found in homozygosis (5 with G183S, 2 with R246W, 1 with G196S, 1 with del642T, 1 with 217_218insC), in three in compound heterozygosis (1 with Q126R/IVS3+1G>A, 1 with Q126R/del418T, 1 with Q126R/G158R) while other three were heterozygous, with only one deleterious mutation (1 with G196S, 1 with A207D, and 1 with R246W). In seven cases, no sequencing abnormalities were detected. The G183S substitution was the most frequently found among miscegenated patients (Afro-Euro-Brazilians) from Bahia. Hormonal and clinical findings did not differ between patients with or without mutations, exception made to a higher frequency of consanguinity and greater severity of genital ambiguity in the first group.

CONCLUSION

Our results reinforce the importance of molecular investigation for the diagnosis of this disease and point out to the finding of a very frequent mutation (G183S) in our series, especially in patients with mixed ethnic background from Bahia, and the description of mutations that have only been reported in Brazilian patients so far.

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.

Sexo cerebral: um caminho que começa a ser percorrido

Fica cada vez mais claro que ocorre um dimorfismo sexual no cérebro de homens e mulheres, e experiências em animais têm mostrado que circuitos específicos se desenvolvem de acordo com o sexo do animal. Desde os trabalhos iniciais de Gorski em ratos, que descreviam o núcleo sexualmente dimórfico na área pré-óptica (SDN-POA), tem sido aceito que, por ação do estradiol, convertido localmente pela aromatase a partir de testosterona, faz-se o imprint para sexo masculino, inibindo-se a apoptose das células do SDN-POA e, portanto, levando a um núcleo anatomicamente maior em machos quando comparado ao de fêmeas. Outras regiões têm mostrado dimorfismo sexual e necessitamos de um marcador para que tais estruturas sejam diferenciadas e possam ser avaliadas na prática clínica. Este dado será de grande valia na atribuição de gênero a pacientes portadores de anomalias da diferenciação sexual, que nascem com ambigüidade genital. Têm havido muitas dúvidas na atribuição do gênero a alguns desses pacientes e não têm sido infreqüentes inadequações sexuais, com mudanças de opções sexuais em época puberal, com grandes traumas tanto para o paciente como para seus familiares. A evolução dos conhecimentos nessa área poderá nos trazer elementos muito importantes para nos auxiliar na atribuição do sexo de criação em vários estados intersexuais e é um caminho que, apesar de estar ainda no seu início, merece ser percorrido.