46, XY Disorder of Sex Development due to 17-Beta Hydroxysteroid Dehydrogenase Type 3 Deficiency in an Infant of Greek Origin.
The development of the male internal and external genitalia in a 46, XY fetus requires a complex interplay of several crucial genes, hormones and enzymes. At the time of fertilization the chromosomal sex is established, which in turn defines gonadal sex and in the final phase of development, phenotypic sex is established by the production and action of specific hormones (1). Among these hormones, testosterone, together with its 5[alpha]-reduced end-product dihydrotestosterone (DHT), plays a crucial role in the development of internal and external genitalia of the male fetus. Testosterone is biosynthesized from cholesterol in five enzymatic steps, the last being the conversion of androstenedione ([DELTA]4) to testosterone that takes place in the testes. This step of testosterone biosynthesis is catalyzed by the enzyme 17-beta hydroxysteroid dehydrogenase type 3 (17[beta]HSD-3). This enzyme is expressed solely in the testes and belongs to a large enzyme family called 17-[beta]-hydroxysteroid dehydrogenase enzymes. Any damaging mutation in the 17[beta]HSD-3 gene (HSD17B3) can cause a 46, XY disorder of sex development (DSD), i.e. a child with a 46, XY karyotype and atypical gonadal or anatomical sex. These mutations can be either homozygous or compound heterozygous and can cause variable 17[beta]HSD-3 enzyme deficiency (2).
Here, we report the case of an infant who presented with ambiguous external genitalia and gonads that were bilaterally palpable in the inguinal region. A 46, XY karyotype was found and 17[beta]HSD-3 deficiency was suspected after measuring a lower than normal testosterone/[DELTA]4 ratio, after a human chorionic gonadotropin (hCG) stimulation test. HSD17B3 gene was genetically analyzed confirming the diagnosis and further validating the idea of a founder effect for 655-1;G[right arrow]A mutation in the Greek population.
The concept of the founder effect is as follows. When a new population is established in a new area by a very small number of individuals, the descendants of this population will show loss of genetic variation. This can be expressed by specific gene mutations being present in the given population, in a much higher frequency than the rest of the world.
The patient was the third baby born to a healthy, non-consanguineous couple of Greek origin. He was born at 37 weeks of gestation by caesarean section with a birth weight of 2860 g and with no perinatal problems. He was referred to our hospital at the age of 23 days due to his ambiguous genitalia at birth. Before referral, his karyotype was determined as 46, XY.
Institutional review board approval was obtained and both the child's parents signed an informed consent in accordance with the national laws. Parents were verbally informed during the investigation regarding the purpose of the study.
On physical examination, he had a phallus-like structure of 1.5 cm, perineoscrotal hypospadias, a perineal blind vaginal pouch and posterior labioscrotal fusion (Figure 1). Two masses, assumed to be the gonads, were palpable in the inguinal canal bilaterally. The rest of the physical examination was normal. Complete blood count and urine analysis were normal. An ultrasound examination confirmed the testicular structure of the masses in the inguinal canals and showed the absence of female internal genitalia.
Baseline LH, FSH, ACTH and cortisol concentrations, measured upon admission, were 12.1 IU/L (0.02-7.0 IU/L), 0.58 IU/L (0.16-4.1 IU/L), 24 pg/dL (5-90 pg/dL) and 11.20 [micro]g/dL (2.8-23 [micro]g/dL), respectively (Table 1). Androgen levels were as follows: [DELTA]4: 10.68 ng/dL (10-37 ng/dL), testosterone: 25 ng/dL (60-400 ng/dL), DHT: 11 ng/dL (12-85 ng/dL) (all normal values given are age-specific). Since baseline hormonal values of various causes of 46, XY undervirilization can significantly overlap, the patient underwent a three-day hCG stimulation test. The results of the test showed a significant increase in [DELTA]4 compared to testosterone and the low testosterone/[DELTA]4 ratio in combination with a normal testosterone/DHT ratio was constistent with a diagnosis of 17[beta]HSD3 deficiency (3).
Mutation analysis of the HSD17B3 gene in the patient was performed using real-time PCR and identified compound heterozygosity of the previously reported missense p.Ser232Leu and the splice junction variant 655-1;G[right arrow]A (Figure 1). Further genetic analysis in both parents revealed the p.Ser232Leu mutation to be inherited from the father and the 655-1;G[right arrow]A from the mother..." (i.e. the double space after A should be corrected).
After discussion with the parents, the decision to raise the child as male was reached. A clinical trial of three doses of 25 mg testosterone enanthate intramuscularly, at four-week intervals was initiated which resulted in an increase in penis size from 1.5 cm to 3 cm (Figure 2). It was proposed that surgical repair of the undescended testes and for correction of the hypospadias be delayed until an appropriate age.
DSD is a group of congenital conditions in which development of chromosomal, gonadal or anatomical sex is atypical. Its incidence is 1 in 5000-5500 (0.018%) (4). The most recent consensus statement on management of intersex disorders classifies DSD in three major categories: sex chromosome DSD, 46,XX DSD and 46, XY DSD (5,6,7).
46, XY DSD comprise cases in which individuals with male chromosomal sex (XY) have atypical gonadal or anatomical sex. 46, XY DSD can be caused by several different defects most commonly involving defective androgen production and/or action. If the testes are normally developed in patients with 46, XY DSD, androgen insensitivity syndrome is usually the cause. Less frequently, 46, XY DSD can be the result of several different mutations involving any of the five enzymes responsible for the conversion of cholesterol to testosterone and its 5[alpha]-reduced end-product, DHT. Among these defects in testosterone production, the most frequent is a deficiency in the 17[beta]HSD-3 enzyme (8). The 17[beta]HSD-3 enzyme is expressed solely in the testes and belongs to a large group of enzymes, the 17-[beta]-hydroxysteroid dehydrogenase enzymes. This family comprises 14 isoenzymes, all of which play a significant role in androgen and estrogen production (3).
17[beta]HSD-3 enzyme deficiency leads to an autosomal recessive form of 46, XY DSD, which was first described in 1971 (9,10). Its precise incidence is unknown, but in a study from the Netherlands it was calculated to be around 1 in 147,000 live births with a heterozygote frequency of 1 in 135 (11). Among populations with a high intermarriage rate, such as the Arabs of the Gaza Strip, the incidence has been reported to be much higher, up to 1 in 100-300 (12,13).
The clinical presentation of individuals with 17[beta]HSD-3 deficiency can vary greatly. Affected males usually present with female external genitalia, fusion of the labia and blind ending vagina, with or without clitoromegaly (Sinnecker types 5 and 4). Less frequently, external genitalia can be ambiguous (Sinnecker type 3), or mainly male with hypospadias and micropenis (Sinnecker type 2) (11,14). Furthermore, phenotypic variation can occur between families with the same homozygous mutation and it seems clear that no specific phenotype is associated with a specific mutation (11). Our patient presented with ambiguous genitalia, with a phallus-like midline structure of 1.5 cm, hypospadias, perineal blind vaginal pouch, posterior labioscrotal fusion, while both his testes were localized in the inguinal canals (Sinnecker type 2 to 3).
Either homozygous or compound heterozygous mutations in the HSD17B3 gene can cause variable 17[beta]HSD-3 enzyme deficiency (4). This gene spans at least 60 kb, consists of 11 exons and is localized on the 9q22 chromosome. To our knowledge, 37 HSD17B3 gene mutations have been reported so far. These include duplication, amplification, intronic splice site and exonic deletion as well as missense and nonsense mutations (2). Some of these appear to be de novo mutations while others are apparently ancient. Since some of the latter have been identified with higher frequency in specific countries or populations, a founder effect has been suggested in several cases (11,15,16).
The phenomenon of founder effect is rather common in the Greek population, and several reports have documented examples of founder mutations in the Mediterranean basin (16,17,18,19). Many previously published reviews cluster the Greeks together with the Turks and the Syrians to show a founder effect regarding the 655-1;G[right arrow]A mutation. According to these papers, this mutation might have spread through the above-mentioned populations during the Ottoman Empire, which extended across most of the Eastern Mediterranean and contributed to the racial admixture in this area (20).
So far, the only reported case of a Greek individual with 17[beta]HSD-3 enzyme deficiency was a paper published in 1978 (21). It describes a 12-year old 46, XY patient reared as a female, with both parents being Greek immigrants residing in New York. The patient was diagnosed with 17[beta]HSD-3 deficiency (termed 17-ketosteroid reductase deficiency at the time) and, later, he was identified to be a homozygote for the 655-1;G[right arrow]A mutation (22). Our patient was a compound heterozygote for mutations in the HSD17B3 gene, having inherited the mutant p.Ser232Leu allele from his father and the 655-1;G[right arrow]A allele from his mother.
In order to have robust evidence of a founder effect in any population, a critical number of individuals presenting with the same mutation for a given genetic trait is needed. Unfortunately, we are describing a rare genetic disease in a rather small ( 11 million) population which is shown by the fact that our patient is only the second Greek individual ever described with 17[beta]HSD-3 deficiency. This makes it very difficult to have more solid evidence.
Nevertheless, the specific mutation (655-1;G[right arrow]A) appears to be present in high frequency in Turks and Syrians, populations that reside in areas that (together with present-day Greece) used to be part of the Ottoman Empire. Thus, it is plausible that these areas of the Eastern Mediterranean were populated by a rather small group of people, which caused some degree of loss of genetic variability. This would lead to an increased number of descendants with specific mutations in some of their genes, even though robust evidence for such founder effects, especially in rare conditions, are yet to be found.
The gender assignment of patients with 17[beta]HSD-3 deficiencies can be quite challenging and necessitates the collaboration of several different medical professionals for the initial decision and the subsequent management plan and follow-up (23). If gonadectomy is withheld, individuals who are reared as females can present in late adolescence with marked virilization due to conversion of the increased amount of [DELTA]4 to testosterone (24). Our patient was partly undervirilized at presentation and showed a good response to the clinical trial of testosterone enanthate as shown by the increase in penis size from 1.5 cm to 3 cm. His parents have been informed about the need for surgical correction of cryptorchidism (around the end of the first year) and hypospadias and microphallus (at least two surgical procedures in the first 2-3 years of life) and are currently satisfied with the development of their son.
We would like to thank the proband and its parents for participating in the study.
Informed Consent: Informed consent from both parents of the proband participating in this paper was obtained in accordance with the national laws.
Peer-review: Externally peer-reviewed.
Concept: Assimina Galli-Tsinopoulou, Design: Assimina Galli-Tsinopoulou, Anastasios Serbis, Nicos Skordis, Data Collection or Processing: Anastasios Serbis, Eleni P. Kotanidou, Eleni Litou, Vaia Dokousli, Konstantina Mouzaki, Analysis or Interpretation: Vassos Neocleous, Pavlos Fanis, Assimina Galli-Tsinopoulou, Nicos Skordis, Literature Search: Anastasios Serbis, Eleni P. Kotanidou, Eleni Litou, Vaia Dokousli, Konstantina Mouzaki, Vassos Neocleous, Writing: Assimina Galli-Tsinopoulou, Anastasios Serbis, Eleni P. Kotanidou, Eleni Litou, Vaia Dokousli, Konstantina Mouzaki, Pavlos Fanis, Vassos Neocleous, Nicos Skordis.
Financial Disclosure: The authors declared that this study received no financial support.
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Assimina Galli-Tsinopoulou (1), Anastasios Serbis (1), Eleni P. Kotanidou (1), Eleni Litou (1), Vaia Dokousli (1), Konstantina Mouzaki (1), Pavlos Fanis (2), Vassos Neocleous (2), Nicos Skordis (2,3,4)
(1) Aristotle University of Thessaloniki Faculty of Medicine, Department of Health Sciences, Papageorgiou General Hospital, 4th Clinic of Pediatrics, Thessaloniki, Greece
(2) The Cyprus Institute of Neurology & Genetics, Department of Molecular Genetics, Function & Therapy, Nicosia, Cyprus
(3) Paedi Center for Specialized Pediatrics, Division of Pediatric Endocrinology, Nicosia, Cyprus
(4) St. George's University of London Medical School at the University of Nicosia, Nicosia, Cyprus
Address for Correspondence: Assimina Galli-Tsinopoulou MD, Aristotle University of Thessaloniki Faculty of Medicine, Department of Health Sciences, Papageorgiou General Hospital, 4th Clinic of Pediatrics, Thessaloniki, Greece Phone: +302310991537 E-mail: email@example.com ORCID ID: orcid.org/0000-0002-8503-3893
[c] Copyright 2018 by Turkish Pediatric Endocrinology and Diabetes Society The Journal of Clinical Research in Pediatric Endocrinology published by Galenos Publishing House.
Confict of interest: None declared
What is already known on this topic?
17[beta]-hydroxysteroid dehydrogenase type 3 (17[beta]HSD-3) enzyme deficiency is a rare cause of ambiguous genitalia in XY neonates due to inadequate testosterone production that leads to undervirilization in utero.
What this study adds?
This study describes a neonate with ambiguous genitalia that proved to be a compound heterozygote for the gene responsible for 17[beta]HSD-3 production and could offer some further validation for the idea of a founder effect for 655-1;G[right arrow]A mutation in the Greek population.
Table 1. Serum androgen concentrations before and after human chorionic gonadotropin stimulation Hormone levels Pre-hCG Post-hCG [DELTA]4 (ng/dL) 136.8 486.4 T (ng/dL) 25 75 DHT (ng/dL) 19.8 22.6 T/[DELTA]4 (n=>0.8) 0.18 0.15 T/DHT (n=<20) 1.26 2.88 hCG: human chorionic gonadotropin, [DELTA]4: androstenedione, T: testosterone, DHT: dihydrotestosterone
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|Title Annotation:||CASE REPORT|
|Author:||Galli-Tsinopoulou, Assimina; Serbis, Anastasios; Kotanidou, Eleni P.; Litou, Eleni; Dokousli, Vaia;|
|Publication:||Journal of Clinical Research in Pediatric Endocrinology|
|Article Type:||Case study|
|Date:||Mar 1, 2018|