Trisomy-X with estrous cycle anomalies in two female dogs

Abstract

Two female dogs were presented with a history of abnormal estrous cycles and infertility, despite multiple breedings. Medical therapy to correct the cycle anomalies did not result in pregnancy. Cytogenetic analysis of blood lymphocyte cultures in each dog revealed three copies of the X chromosome in each cell, constituting a 79,XXX karyotype (trisomy-X). Both dogs were eventually ovariohysterectomised and histological evaluation revealed hypoplastic ovaries and an absence of normal follicular structures. However, partial or immature follicles were noted, which may have been sufficient to cause both females to initiate cycling. The history and clinical characteristics found in these dogs were compared to those described in three other dogs reported with trisomy-X, as well as those reported in other species. These findings highlighted the importance of cytogenetic studies in fertility evaluation and achieving a definitive diagnosis for infertility in the bitch.

Fig. 1

(Case 1) A. Photomicrographs of ovary and cross sections of the uterine tube (arrows) within the wall of the ovarian bursa. Both ovaries were small with relatively thin cortices (bilateral ovarian hypoplasia). B) Higher magnification of the cortex in section of ovary from 1A. Normal appearing subepithelial structures (SES; arrow) were present, but there is an absence of normal follicular structures. Poorly differentiated sex cords (arrowheads) were present deeper in the parenchyma. C) Higher magnification of immature sex cords, which varied from poorly differentiated follicle-like structures (large arrows) that did not contain oogonia or oocytes, to those resembling poorly differentiated seminiferous tubules (arrowhead).

Figure 2

(Case 2) Photomicrograph of the cortex and superficial medulla of one ovary, with subepithelial structures and prominent cross sections of immature sex cords. The latter ranged in morphology from poorly differentiated follicles without oocytes (large arrow) to smaller structures that resembled poorly differentiated seminiferous tubules (arrowheads). Histologic features of the contralateral ovary were similar.

Fig. 3

Metaphase spread from peripheral blood lymphocyte culture (Dog 1) demonstrating a 79,XXX (trisomy X) karyotype. The X chromosomes were indicated (arrow).