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Introduction  

Cryptorchidism is a defect which occurs in many species and, in most of them, can be diagnosed at birth. In dogs, However, the testes are still inside the abdomen at birth, reaching their final position in the scrotum at 35 to 40 days later (3).

Specific causes of cryptorchidism in the dog are unknown (4). A disorder of MIF (Mullerian Inibitor Factor) secretion has been hypothesized in miniature Schnauzers as causing the presence of both a uterus and cryptorchidism (5). Canine cryptorchidism has been described as a sex-limited trait (6,7)  and is mostly bilateral. A single autosomal recessive gene has been cited as a probable cause(6). The wide breed distribution  of cryptorchidism in the dog suggests that inheritance may not be the only factor (8).

Klinefelter syndrome is the most common form of primary testicular failure involving both spermatogenesis and androgen secretion, and has been reported in man(9,10) and many other mammalian species: mouse (11), Chinese hamster (12), pig (13), bull (14), sheep (15), goat (16), horse (17), cat (18) and dog (5,19,20,21). Most  XXY humans are phenotypic males (22) and most of the XXY dogs have been described as intersex animals (23).

The XY/XXY complement, was presented as a variation of the Klinefelter syndrome(1) , and in this condition, the secondary sex characteristics were less affected than in patients with XXY syndrome.

The present paper describes a Poodle dog with bilateral cryptorchidism, associated with 78,XY/79,XXY mosaicism.

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Materials and Methods  

A one year old male Poodle was detected with bilateral cryptorchidism. Metaphase chromosomes were prepared from peripheral blood lymphocyte culture (24). Cells from the two gonads were cultured for cytogenetic investigation (25). Histological sections were prepared from the testis and stained with haematoxylin and eosin.

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Results  

Cytogenetic analysis showed a 78,XY/79,XXY chromosome complement (figure 1). This mosaicism was both on peripheral blood lymphocyte culture and gonadal tissue. Lymphocyte analysis revealed 18% of metaphases 79,XXY. The right testis showed 30% of cells 79,XXY while the left one presented 12%.

Histopathological study of both gonads revealed testis with expressive vacuolation of the seminal cells and total absence of sperm cells (figure 2) The interstitium appeared relatively slaked, revealing in a few microscope fields, small nests of Leydig cells (figure 3).    

FIGURE 1:  Two metaphases (prepared from peripheral blood lymphocyte culture) at the same microscope camp: one of them with XY sexual chromosomes and other with XXY sexual chromosomes, demonstrating the mosaicism in a poodle dog with bilateral cryptorchidism. Arrows indicate the sex chromosomes.

FIGURE 2:  Photomicrogaph of an H&E stained section of testis from a Poodle with cryptorchidism and mosaicism 78,XY/79,XXY, demonstrating expressive vacuolation of the seminal cells and total absence of sperm cells.

FIGURE 3: Photomicrograph of H&E-stained section of testis from the same dog, showing small nests of Leydig cells and a relatively slaked interstitium.

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Discussion

Bilateral cryptorchidism in dogs was associated with the Klinefelter syndrome in the past (5) and also with 78,XY/79,XXY chromosome constitution. The presence of mosaicism reveal the absence of mitotic disjunction at some time during embryonic development.

The variant form of Klinefelter’s syndrome more frequently found is the XY/XXY mosaicism (1). The influence of the normal cell in modifying the full expression of this syndrome, will be illustrated by contrasting the findings in patients with XY/XXY mosaicism with those in patients with the classic form. In some patients, the XXY cell line could be identified only in testicular tissue, reinforcing the requirement of cytogenetic investigation in dogs with cryptorchidism

The fact that the right testis presented higher number of 79,XXY cells (30%) than  the left testis (12%), is probably related to the cell distribution in the gonad during embryonic development and did not reflect morphological differences between the gonads.

The distance covered by the testis into the scrotum is greater in dogs than in man. Although the cryptorchidism may be considered rare in the human Klinefelter syndrome (27), in dogs it may be more frequent.

The descent process of the testis in dogs is going from a localization near the kidneys until the scrotum and doesn’t occur in the prenatal phase like in other species including the human beings (4).

Many experiments have been performed to identify the factor responsible for the descent of the testis in dogs. There are indications that the activity of the gubernaculum testis or the consequent descent of the testis is regulated by an androgenic factor, not yet identified, secreted by the Sertoli cells or germ cells and that testosterone has an important action on the regulation of gubernacular regression at the intra-inguinal phase of descent (26).

The Leydig cells, responsible by testosterone production are histologically and functionally abnormal in Klinefelter’s syndrome. The abnormal functioning of these cells are evident in individuals with Klinefelter’s syndrome by low levels of plasmatic testosterone and low response to GCH administration (gonadotrophine corionic hormone) (27).

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References

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