Introduction
Disorders of sexual development (DSD) are classified according to the stage of embryonic or fetal sex differentiation and are designated as chromosomal, gonadal, or phenotypic (Poth et al., 2010; Meyers-Wallen, 2012). During genitalia development, changes in the production or function of Müllerian inhibitory substance (MIS), testosterone, insuline-like 3 (INSL3), Specific MIS type II receptor (MISRII), or iatrogenic masculinization in pregnant females may result in phenotypic DSD. In these individuals, chromosomal sex and gonadal sex are correct, but the external or internal genitalia do not correspond to them (Meyers-Wallen, 2009).
Pseudohermaphroditism is a rare anomaly. It occurs when chromosomal and gonadal sexes are equivalent, but there is a mismatch or ambiguity in the phenotype. Male or female pseudohermaphrodite are linked according to gonadal sex. Two types of male pseudohermaphroditism have been described, each one with distinct etiologies: impaired androgen- dependent masculinization and persistent Müllerian duct syndrome (PMDS) (Cristensen, 2012). The PMDS is considered a hereditary disease inherited as an autosomal recessive trait in miniature Schnauzer and Basset hound, also reported in other breeds (Poth et al., 2010; Breshears and Peters, 2011). PMDS can be triggered by faults in production or function of the Müllerian inhibitory substance or by specific receptors of the same (MISRII) in the Müllerian ducts (Meyers-Wallen, 2009). Affected individuals have male chromosomes (78, XY) and present uterine tubes, a uterine body, cervix and cranial vagina, as well as internal and external male organs (Meyers- Wallen et al., 1989).
Diagnosis of sexual development disorders in dogs has great clinical and epidemiological importance; however, few reports hinder the epidemiological, pathophysiological, and genetic study of these abnormalities, challenging the diagnostics, therapeutics, and prevention for clinical and obstetric routine. Therefore, this report describes the diagnostic findings and treatment performed on a Yorkshire terrier presenting persistent Müllerian duct syndrome.
Patient examination
Anamnesis.
A one-year-old female Yorkshire terrier, weighing 2.2 kg, with an abnormal structure in the inguinal region was presented for clinical evaluation at the Hospital Veterinário “Governador Laudo Natel”, Unesp-Jaboticabal, SP, Brazil. The owner denied similar changes in parents or siblings.
Clinical and laboratorial findings.
At physical examination of the inguinal region, a preputial orifice with a small structure similar to a penis was observed protruding from the canal in flow direction (Figure 1A). It presented an external urethral orifice immediately at the transition between the base and the pseudopenis (Figure 1B). The protrusion was not identified as other external genital structure.
At abdominal ultrasound examination, caudally to the urinary bladder, an echogenic, elongated and bilobed structure involving the pelvic urethra was observed, suggesting the presence of prostatic tissue (Figure 2A). In the right retroperitoneal region there was an isoechogenic rounded-up structure in relation to splenic tissue, with architecture similar to the testis (Figure 2B); however, there were not any recognizable reproductive structures in the left region. Complementarily, radiographic examination of the perineal area showed a mineral-dense structure (radiopaque) corresponding to the rudimentary penis bone (Figure 2C).
Karyotyping analysis.
Additionally, cytogenetic analysis of 100 metaphase cell preparations obtained from a patient’s leukocyte culture was conducted, and the chromosomes were observed in Giemsa-stained preparations. The karyotype of this patient consisted of 38 pairs of autosomal acrocentric chromosomes, one metacentric X chromosome and one submetacentric Y chromosome (78, XY), considered normal for a male of the species Canis familiares. Chimerism and mosaics were discarded, considering the number of metaphases analysed. The phenotypic changes, karyotype (78, XY), bilateral testis, uterine horns and uterine body correlate with abnormalities of sexual differentiation, consistent with PMDS.
Treatment approach .
After analysis of the findings, the initial suggested diagnosis was a sexual development disorder, such as pseudohermaphroditism. Then, an exploratory laparotomy was conducted to confirm and complete resection of the internal genital structures. Two structures macroscopically similar to the testicles were observed: one in the caudal region of the right kidney and the other in the left kidney. These tissues were connected to two structures similar to the uterine horns, caudally fused into one body and cervix that entered in the pelvic cavity. All tissue was removed and submitted for histopathologic examination.
Corrective surgery was then performed to cover the penile tissue and avoid damage by exposure and contact. The urethral orifice was carefully positioned in the region free of the opening. To ensure proper healing, the urethra remained probed for five days. Satisfactory recovery was observed during the postoperative clinical examination, and one year later the animal appears healthy, with no further history of clinical genitourinary complications.
Histology revealed the presence of typical seminiferous tubules, interspersed in Leydig cells infiltrate and light peritubular fibrosis, increased genital tubules with atrophic mucosa and the muscle layer, typically defined as testicular parenchyma and structures compatible with uterine tubes (Figure 3) characterized by proliferative endometrial glands. No ovarian tissue was found.
Discussion
As previously described, PMDS is a disorder of the phenotypic sexual development that rarely affects other breeds besides the miniature Schnauzer and Basset hound (Poth et al., 2010). Regarding the Yorkshire terrier, to our knowledge, this anomaly is rare; other researchers described a two-year-old animal with clinical, chromosomal, and internal genital characteristics similar to the present case; however, the external phenotype was intermediate between male and female; histologically, testicles had hyperplasia of Leydig and seminoma cells, and the animal showed male behaviours such as territorial marking and breeding inanimate objects (Hagel et al., 2010).
Differences regarding behaviour are related to the age of the patient. After puberty, testes and genitalia increment their function and concomitant diseases, such as Sertoli cell tumor, hydrometra, cystic endometrial hyperplasia, pyometra, cystitis, and epididymal malformations commonly develop (Marshall et al., 1982; Whyte et al., 2009; Vegter et al., 2010).
The specific diagnosis of this syndrome was based on a dog with karyotype 78, XY and the presence of both testicles and internal female genital organs verified by histopathology (Meyers-Wallen, 2009). Previous reports determined that these patients were SRY-positive (Hagel et al., 2010). However, this test was not performed when addressing this case as both gonads corresponded to normal testicles, and this demonstrates the expression and function of the gene. For diagnosing a specific genetic ethology, molecular and proteomic tests would be needed to assess mutation of the MSIRII receptor as well as MIS expression and function (Meyers-Wallen, 2009). Nevertheless, in a clinical context, the diagnostic approach performed in this case allowed the DSD determination and male 78, XY phenotypic classification coincident with PMDS features.
The recommended treatment for this abnormality is gonadectomy and internal genitalia excision to avoid or correct common complications described above (Meyers-Wallen, 2009). Regarding external genitalia, the treatment should be instituted according to the needs of each patient and determined in agreement with the owner. Penectomy or clitoridectomy associated with ureterostomy are commonly imposed in these malformations, but this approach was considered an invasive, risky, and dispensable technique in our patient since the pseudo-penis structure did not compromise any organic function that could pose a health risk (Borrow et al., 2011; MacPhail, 2013). Therefore, corrective surgery was conducted to cover, protect, and prevent dryness, ulceration or infection of the penile structure, as indicated for treating paraphimosis (Pavletic and O’Bell, 2007; Fossum, 2008).
Conclusion
Sexual development disorders represent a diagnostic and therapeutic challenge in small animal practice. The PMDS is an unusual anomaly, especially in Yorkshire terrier breeds. This report, which presents a diagnostic and therapeutic approach to PMDS, can be a valuable tool for clinical, epidemiological, and scientific studies on small animal practice, reproduction, and genetics.