Telvi L, Lebbar A, Del Pino O, Barbet J P, Chaussain J L
Laboratoire de Cytogénétique, Hôpital Saint Vencent de Paul, 82, avenue Denfert Rochereau, 75674 Paris Cedex 14, France.
Pediatrics. 1999 Aug;104(2 Pt 1):304-8. doi: 10.1542/peds.104.2.304.
There exist substantial differences between prenatally and postnatally diagnosed cases of 45,X/46,XY mosaicism. Ninety percent of prenatally diagnosed cases show a normal male phenotype, whereas the postnatally diagnosed cases show a wide spectrum of phenotypes. This 10% risk of an abnormal outcome in prenatally diagnosed cases requires further attention. The purpose of the present study is to provide more information on the postnatally diagnosed 45,X/46,XY mosaicism cases. To date, only a few series have been reported. An accurate diagnosis in these patients is essential not only to their follow-up, but also to providing appropriate genetic counselling and subsequent prenatal diagnosis to their parents.
The clinical, cytogenetic, endocrinologic, histologic and molecular biological findings of 27 patients with 45, X/46,XY mosaicism are analyzed.
The reported cases showed a wide spectrum of phenotypes as Turner syndrome, mixed gonadal dysgenesis (MGD), male pseudohermaphroditism (MPH) and apparently normal male. However, Ulrich-Turner stigmata were the most common features found in this series. Patients with MGD or MPH presented with various degrees of sex reversal such as hypospadias and/or abnormal internal genitalia. No correlation between the proportion of the 45,X/46,XY cell lines in the blood or the fibroblasts and the phenotype was found. Mild mental retardation was present in 4 of the patients and 2 patients showed signs of autism.
Two major points are emphasized in this series: 1) the presence in 7 histologically analyzed streak gonads of a homogeneous 45,X chromosomal complement suggests that the invasion of the primitive genital ridge by a such a cell line may induce abnormal gonadal development; 2) 3 males, apparently normal at birth, developed late onset abnormalities such as dysgenetic testes leading to infertility, Ulrich-Turner stigmata, dysmorphic features, and mild mental retardation. These data indicate the importance of an accurate clinical and histologic evaluation of any patient presenting with 45, X/46,XY mosaicism.
45,X/46,XY嵌合体的产前诊断病例和产后诊断病例之间存在显著差异。90%的产前诊断病例表现为正常男性表型，而产后诊断病例表现出广泛的表型。产前诊断病例中有10%出现异常结果的风险需要进一步关注。本研究的目的是提供更多关于产后诊断的45,X/46,XY嵌合体病例的信息。迄今为止，仅有少数系列报道。对这些患者进行准确诊断不仅对其随访至关重要，而且对为其父母提供适当的遗传咨询和后续产前诊断也至关重要。
分析了27例45,X/46,XY嵌合体患者的临床、细胞遗传学、内分泌学、组织学和分子生物学检查结果。
报道的病例表现出广泛的表型，如特纳综合征、混合性性腺发育不全（MGD）、男性假两性畸形（MPH）以及外表看似正常的男性。然而，乌尔里希-特纳体征是本系列中最常见的特征。MGD或MPH患者表现出不同程度的性反转，如尿道下裂和/或内生殖器异常。未发现血液或成纤维细胞中45,X/46,XY细胞系比例与表型之间存在相关性。4例患者存在轻度智力障碍，2例患者有自闭症迹象。
本系列强调了两个要点：1）在7个经组织学分析的条索状性腺中存在均一的45,X染色体组成，这表明这样的细胞系侵入原始生殖嵴可能会诱导性腺发育异常；2）3名出生时外表看似正常的男性出现了迟发性异常，如性腺发育不全导致不育、乌尔里希-特纳体征、畸形特征和轻度智力障碍。这些数据表明，对任何表现为45,X/46,XY嵌合体的患者进行准确的临床和组织学评估非常重要。
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