Cytogenetics and Molecular Genetics Division, Prince Sultan Military Medical City, Riyadh, Saudi Arabia.
Cytogenetics and Molecular Genetics Division, Prince Sultan Military Medical City, Riyadh, Saudi Arabia.
Eur J Med Genet. 2021 Jul;64(7):104225. doi: 10.1016/j.ejmg.2021.104225. Epub 2021 Apr 16.
Ring X is a chromosomal anomaly mainly seen in females with turner syndrome and usually present in mosaic form with 45,X cells (45,X/46,X,r(X)) because of their mitotic instability. In males it is an extremely rare finding because large nullisomy for X chromosome material is likely not compatible with survival. Only two cases of male with ring chromosome X were previously reported. We report here a four-year-old male with ring chromosome X characterized using Karyotype, FISH and array CGH and presenting short stature, microcephaly and hypospadias. Molecular investigations showed 923 Kb terminal deletion on the pseudoautosomal region 1 (PAR1) including SHOX gene followed by a duplication of 2.4 Mb. The absence of functional nullisomy because of a second copy of deleted genes was present in chromosome Y PAR1 region may explain the compatibility with survival in our case of male with ring X. Short stature common with the two previously reported cases is likely related to SHOX gene deletion but also to the effect of "ring syndrome". However, hypospadias was not reported in the previous cases and can be due to the associated duplication outside PAR1 region including in particular PRKX gene coding for a protein involved in urogenital system morphogenesis.
X 染色体环是一种主要见于特纳综合征女性的染色体异常，通常以嵌合体形式存在，具有 45,X 细胞（45,X/46,X,r(X)），因为它们的有丝分裂不稳定。在男性中，这是一种极其罕见的发现，因为 X 染色体物质的大片段缺失很可能与存活不相容。以前只报道过两例男性 X 染色体环。我们在此报告一例四周岁男性 X 染色体环，通过核型分析、荧光原位杂交和 array CGH 进行特征描述，表现为身材矮小、小头畸形和尿道下裂。分子研究显示，假常染色体区域 1（PAR1）上存在 923kb 的末端缺失，包括 SHOX 基因，随后是 2.4Mb 的重复。由于 Y 染色体 PAR1 区域存在缺失基因的第二个拷贝，因此不存在功能性的单体缺失，这可能解释了我们的 X 染色体环男性病例的存活相容性。与之前报道的两例病例一样，身材矮小可能与 SHOX 基因缺失有关，但也与“环综合征”有关。然而，尿道下裂以前没有在以前的病例中报道过，可能与 PAR1 区域以外的相关重复有关，包括特别是编码参与尿生殖系统形态发生的蛋白质的 PRKX 基因。
