46 XX karyotype during male fertility evaluation; case series and literature review.

Forty-six XX disorder of sex development is an uncommon medical condition observed at times during the evaluation of a man's fertility. The following is a case series and literature review of phenotypically normal men diagnosed with this karyotype. Our goal is to comprehend the patients' clinical presentation as well as their laboratory results aiming to explore options available for their management. A formal literature review through PubMed and MEDLINE databases was performed using "46 XX man" as a word search. A total of 55 patients, including those conveyed in this article were diagnosed with a 46 XX karyotype during their fertility evaluation. The patients' mean age ± s.d. was 34 ± 10 years and their mean height ± s.d. was 166 ± 6.5 cm. Overall, they presented with hypergonadotropic hypogonadism. Sexual dysfunction, reduced hair distribution, and gynecomastia were reported in 20% (4/20), 25.8% (8/31), and 42% (13/31) of the patients, respectively. The SRY gene was detected in 36 (83.7%) and was absent in the remaining seven (16.3%) patients. We found that a multidisciplinary approach to management is preferred in 46 XX patients. Screening for remnants of the mullerian ducts and for malignant transformation in dysgenetic gonads is imperative. Hypogonadism should be addressed, while fertility options are in vitro fertilization with donor sperm or adoption.

INTRODUCTION

Infertility is a common medical problem affecting roughly one out of six couples.1 A male factor is either responsible for or contributory to about half the cases.2 Once conception fails to occur after at least 12 months of regular unprotected intercourse, the couple's fertility is often investigated. Genetic testing in men has a distinctive set of indications that are usually picked up during the initial workup. Marked reduction of sperm concentration, unilateral/bilateral absence of vas deference, and suggestive family history are influential factors. Chromosomal abnormalities occur in <1% of the general population,3 however their incidence rises up to 15% in men with infertility.4

The 46 XX testicular disorder of sex development (DSD), previously known as de la Chapelle syndrome after its first report in 1964,5 comprises a small share of genetic causes of male infertility. It is a rare condition occurring in about 1:20 000 males6 and characterized by a variable degree of mismatch between the phenotype and the genotype of the affected individual. Patients may present seeking fertility with normal male internal and external genitalia, or may present at an earlier age because of ambiguous genitalia. Undescended testes, micropenis, and hypospadias are commonly reported,7 as well as residual remnants of the mullerian tract.8 What preserves a male phenotype in these individuals is translocation of the sex-determining region Y gene (SRY) into a sex chromosome or an autosome, a process occurring in about 80% of cases.9 In the remaining SRY-negative patients, presumed hidden mosaicism for the SRY gene or possible mutation of inhibitors of the male pattern has been postulated.9

In this study, we report a series of cases of 46 XX men presenting with infertility and perform a formal literature review of similar cases aiming to provide a comprehensive approach for managing this relatively rare condition.

PATIENTS AND METHODS

We reviewed the records of patients presenting for initial male fertility evaluations during the period from 2011 to 2015 at two institutions (Cleveland Clinic and Hamad Medical Center). We identified six patients who were found, with genetic testing, to have 46 XX karyotype. The patients’ medical records were checked for information regarding their presentation, significant medical problems, biologic data, physical examination, and laboratory investigations.

Semen analysis

All patients were evaluated with semen analysis and hormonal profile. The semen analysis was performed after 3–5 days of sexual abstinence. Collection is done through masturbation into a clean container. Samples were incubated at 37°C and allowed to liquefy for 30 min before analysis. The analysis was performed according to the WHO guidelines adopted in 2010.10

Hormone profile

Hormones investigated constituted of follicular stimulating hormone (FSH) (normal level [nl]: 1–9 IU l−1), luteinizing hormone (LH) (nl: 1–9 IU l−1), prolactin (nl: 2–14 ng ml−1), total testosterone (nl: 220–1000 ng dl−1), and estradiol (nl: 10–60 pg ml−1).

Cytogenetic and FISH investigations

Genetic testing in the form of karyotype and Y chromosome micro-deletion analysis was performed on all patients according to practice guidelines. A conventional chromosome analysis was performed from patients’ peripheral blood lymphocytes, which were cultured in RPMI 1640 medium, phytohemagglutinin, and fetal bovine serum for 72 h, followed by treatment with 50 μg ml−1 colcemid. Metaphase chromosome spreads were studied by standard GTG and CBG banding procedures, which included using trypsin and Giemsa for G-banding and barium hydroxide for C-banding. FISH was performed on thirty metaphase chromosome spreads using a mixture of probes specific for DXZ1 and DYZ3, and a chromosome-specific probe for CBFB GLP 16 banding at 16q22. Multiplex PCR amplification of nine sequence-tagged site markers was used to detect AZF region micro-deletions on the Y chromosome.

Literature review

A formal literature review was performed using PubMed and MEDLINE databases for the period from 1964 to 2015. The search word “46 XX man” was used. Search results were reviewed for relevance and quality. The inclusion criteria were studies reporting adult patients presenting with infertility and in English language. Case reports of patients of pediatric age group as well as those investigated for reasons other than infertility were excluded. The Institutes’ Ethics Committee accepted the research, and a waiver of signed informed consent was used.

RESULTS

Six patients were found to have 46 XX karyotype and were included in this study. The patients’ mean age ± s.d. was 34.3 ± 4.5 years. A normal male phonotype was detected in all except one patient who had a eunuchoid habitus characterized by increased fat distribution, reduced virilization, and gynecomastia. The patients’ mean testicular volume ± s.d. was 5.5 ± 1.8 ml. All patients presented with primary infertility and had normal volume azoospermia on semen analysis. Hormone analysis revealed hypergonadotropic hypogonadism with a mean testosterone, FSH, and LH ± s.d. of 158.8 ± 107 ng dl−1, 22.2 ± 11.2 IU l−1, and 14.2 ± 5.7 IU l−1, respectively. FISH confirmed the presence of a translocated SRY region on the long arm of the X chromosome in five patients and its absence in the sixth patient. Other characteristics of their presentation are shown in .

The literature search resulted in 152 articles. After meticulous review, 29 papers met the inclusion criteria and contained 49 patients with 46 XX DSD. displays all literature cases, including those reported in this study, of 46 XX men diagnosed during fertility evaluation. The reported mean age ± s.d. was 34 ± 10 years. Sexual dysfunction, reduced hair distribution, and gynecomastia were reported in 21% (4/19), 26.6% (8/30), and 40% (12/30) of patients, respectively. Patients’ mean height ± s.d. was 166 ± 6.5 cm. Overall, patients had hypergonadotropic hypogonadism with a mean testosterone ± s.d. of 274.3 ± 135.3 ng dl−1, mean FSH ± s.d. of 40.4 ± 22.2, and mean LH ± s.d. of 23.4 ± 13.4. FISH was performed in 43 patients. The SRY gene was detected in 36 (83.7%) and was absent in the remaining 7 (16.3%) patients. The translocation was to a sex chromosome in 95% (38/40) and to an autosome in 5% (2/40) of the patients. In two out of the seven SRY-negative patients, the authors investigated the DAX1 and SOX9 genes and failed to detect any mutation. Testicular atrophy was reported in all cases while testis biopsy was performed in ten patients and showed absence of spermatogenesis with Sertoli cell only and Leydig cell hyperplasia.

DISCUSSION

46 XX DSD is a genetic abnormality infrequently encountered by andrologists during fertility evaluation of phenotypically normal males. Once encountered, a thorough understanding of all its implications is mandatory for adequate management and counseling. Several etiologic theories have been proposed to help understand this condition. In SRY-positive patients, cross-over between pseudoautosomal regions of sex chromosomes is believed to occur during paternal meiosis.11 Whereas in SRY-negative patients, the link remains unclear. Some have advocated the presence of different sex determining genes located on autosomes initiating “maleness.”12 For example, SOX9 gene, which is located on the long arm of chromosome 17, is known to potentiate SRY gene effects and its overexpression has been linked to 46 XX SRY-negative males.13 Others believe that the SRY gene is in fact inhibitory to other autosomal genes, termed “Z” genes, that are themselves inhibitory to male sex determination.14 Furthermore, an X-linked dosage-sensitive sex reversal locus has been identified and functions as a repressor of male pathway. Meeks et al. confirmed that mutations to the DAX1 gene would lead to 46 XX female-to-male sex reversal.15 Of all the cases of 46 XX DSD reported in men seeking fertility, the SRY gene was present in 83.7% and absent in 16.3%. Two cases performed PCR amplification of the SOX9 and DAX1 regions and failed to find any mutation. Unfortunately, these mutations were also not assessed in our SRY-negative patient.

A number of characteristic features are picked up during physical examination but are not sufficient to make a diagnosis. Unlike Klinefelter patients (47 XXY) who can present with similar complaints, patients with 46 XX DSD generally have a short stature which is mainly due to lack of testosterone-driven pubertal growth spurt or due to absence of other Y-chromosome specific growth factors.16 The mean height ± s.d. of reported cases in this review was 166 ± 6.5 cm. The degree of virilization is variable. While it is complete in some patients, others may have poor hair growth, female fat distribution, and gynecomastia secondary to an altered testosterone/estradiol ratio. This imbalance is thought to result from an increase in peripheral aromatization of testosterone. A finding that is influenced by the increase in fat mass and the decrease in lean muscle mass, which is often seen in many chromosomal disturbances with subsequent hypogonadism.17 This variability can be explained by the hypogonadism often in existent or may be secondary to a dose-dependent genetic aberration, as has been postulated by some researchers.18 Up to 40% of cases had some form of reduced virilization.

Testicular atrophy is always detected on genital examination, in addition to other less frequent abnormalities such as undescended testis and hypospadias,19 which have been reported in 5.5% and 7.4% of cases in this review.

Azoospermia is present on semen analysis as would be expected since all Y chromosome azoospermia factors (AZF) are lacking.20 Serum hormone testing reveals hypergonadotropic hypogonadism consistent with primary testicular failure. The mean ± s.d. of serum testosterone, FSH, and LH reported in all cases were 274.3 ± 135.3 ng dl−1, 40.4 ± 22.2 IU ml−1, and 23.4 ± 13.4 IU ml−1, respectively. Once karyotype analysis fails to detect a Y chromosome in a phenotypic male, FISH or molecular amplification by polymerase chain reaction (PCR) is performed to look for the presence or absence of SRY gene. Although this workup does not have a prognostic value, it documents the various genetic rearrangements of the syndrome. SRY-negative patients are believed to have a higher frequency of genital ambiguities,21 this particular association was not found in this subset of 46 XX DSD patients.

A multidisciplinary approach to management is favored after reaching the diagnosis. Genetic counseling is required to help the patient and his partner understand various aspects of his condition, in addition to psychological support, which would ease his comprehension of difficult information. Imaging of the pelvis is required to look for remnants of mullerian ducts that may cause morbidity in the form of repeated infections or urinary incontinence22 and require surgical removal. Neoplastic transformation (gonadoblastoma) of dysgenetic gonads has been described in up to 30% of cases specifically when Y chromosome material is detected.23 As such, serial self-examinations should be encouraged together with regular gonadal ultrasound imaging. Repeated gonadal biopsy and even gonadectomy in nonfunctioning gonads have also been proposed to overcome the risk of malignancy.24 Testicular biopsy has been reported in ten cases displaying unified absence of germinal cells and Leydig cell hyperplasia.12252627282930313233 Surgical correction of genital ambiguities such as hypospadias and undescended testis is required. Cosmetic surgery for gynecomastia should also be considered if the patient desires.

The patient's hypogonadism should be managed with testosterone replacement. Therefore, discussion about different forms of testosterone therapy and their possible side effects should be considered early after diagnosis. Prior to initiating therapy, a baseline bone density scan (DEXA) should be performed to look for osteopenia or frank osteoporosis. Patients with a T score of <−1.0 would benefit from treatment with Vitamin D and calcium, bisphosphonates, or calcitonin, and require annual repeats of DEXA scan until results are normal.19 As regards to fertility, options are limited to artificial insemination or in vitro fertilization using donor sperm or resolving to adoption.

CONCLUSION

46 XX DSD is a rare genetic disorder that is seldom picked up during evaluation of patients with infertility. An understanding of all aspects of this condition is certainly required for offering the most suitable treatment. Herein, we report the largest single report case experience as well as the largest review of worldwide experience with 46 XX DSD detected during fertility evaluation.

AUTHOR CONTRIBUTIONS

AM participated in the acquisition of data, summarized the collected evidence, and drafted the manuscript. MA designed the study and participated in the acquisition of data. SC participated in the acquisition of data. HA revised the manuscript and helped in coordination. SA revised the manuscript and helped in co-ordination. ES helped to draft the manuscript and provided supervision. All authors read and approved the final manuscript.

COMPETING INTERESTS

The authors declare no competing interests.

Table 1

46 XX DSD men presenting with infertility