Sinovich Matthew, Monné Rodriguez Josep, Pieńkowska-Schelling Aldona, Schelling Claude, Kelly Padraig G
The Liphook Equine Hospital, Forest Mere, Liphook, UK,
Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Sex Dev. 2025 Apr 8;19(1):1-9. doi: 10.1159/000545559.
Monorchidism is a rarely described condition in the horse and is not to be confused with cryptorchidism. The diagnosis is challenging and confirmed by surgery and histology in combination with hormonal assays. This report describes, to the best of the author's knowledge, the first case of monorchidism and abdominal cryptorchidism of the developed testicle in a horse.
An Irish Cob underwent laparoscopic castration for removal of bilateral cryptorchid testicles. At surgery, the horse was diagnosed as a monorchid with the testicle retained intra-abdominally. Histopathological, hormonal, molecular and cytogenetic analysis was performed. This included measuring testosterone and anti-Mullerian hormone (AMH) in serum blood, isolating genomic DNA from EDTA- and heparin-treated blood, PCR amplification of the SRY gene, metaphase chromosome preparation, and DAPI banding before metaphase analysis with fluorescence in situ hybridisation (FISH) analysis.
The horse was positive for the SRY gene and had a mosaic 63,X/64,XY karyotype with the aneuploid cells being present in only 2% of metaphases. FISH showed that the missing sex chromosome of the aneuploid cell line was the Y chromosome embedded in micronuclei. An abnormal high rate of micronuclei (6.6%) was observed indicating genotoxic events and/or genome instability. Hormonal assay results confirmed that AMH was not significantly increased, suggesting that no further testicular tissue was present. Histopathology was consistent with testicular tissue displaying a Sertoli cell-only pattern with bipolar ductal structures.
The exact causes of monorchidism and cryptorchidism are unclear, but the elevated rate of micronuclei is clear evidence for genome instability which might have been involved in the failure of normal testicular development and descent. Future cases could further clarify the disease mechanism based on this report.
单睾症在马匹中是一种鲜有描述的病症，不应与隐睾症相混淆。其诊断具有挑战性，需通过手术、组织学检查并结合激素检测来确诊。据作者所知，本报告描述了首例马匹单睾症及发育正常的睾丸腹腔内隐睾症病例。
一匹爱尔兰科布马接受了腹腔镜去势手术，以切除双侧隐睾。手术中，该马被诊断为单睾症，睾丸保留在腹腔内。进行了组织病理学、激素、分子和细胞遗传学分析。这包括测定血清中的睾酮和抗苗勒管激素（AMH），从乙二胺四乙酸（EDTA）和肝素处理的血液中分离基因组DNA，SRY基因的聚合酶链反应（PCR）扩增，中期染色体标本制备，以及在中期分析前用荧光原位杂交（FISH）分析进行DAPI染色。
该马SRY基因呈阳性，具有63,X/64,XY嵌合核型，非整倍体细胞仅占中期细胞的2%。FISH显示非整倍体细胞系缺失的性染色体为嵌入微核的Y染色体。观察到微核率异常高（6.6%），表明存在基因毒性事件和/或基因组不稳定。激素检测结果证实AMH没有显著升高，提示不存在更多的睾丸组织。组织病理学结果与睾丸组织呈现仅支持细胞模式并伴有双极导管结构一致。
单睾症和隐睾症的确切病因尚不清楚，但微核率升高是基因组不稳定的明确证据，这可能与正常睾丸发育和下降失败有关。未来的病例可基于本报告进一步阐明疾病机制。
