![]() ![]() However, development of a complete fetus does not happen, suggesting later problems with proper fetal differentiation. In a partial hydatidiform mole, this maternal X signal is present. As speculated under complete hydatidiform mole, the presence of the maternal X chromosome in the triploid set may be the signal that limits differentiation. Unlike the complete hydatidiform mole, where morula differentiation to a chorion and amnion fails, a partial hydatidiform mole has clear fetal elements. If a triploid karyotype is determined, 69,XXX, 69XXY, or 69 XYY, a partial mole can then be confirmed. After spontaneous abortion or dilation and curettage tissue needs to be examined by pathology and cytogenetics determined. Ultrasound, however, is strictly an indicator. Partial hydatidiform mole can be indicated by ultrasound showing placenta tissue, some hygromatous cysts, and some fetal oddments but no clear fetal structure. It could be said that a complete hydatidiform mole is a consequence of an anucleate ovum, and a partial hydatidiform mole is the consequence of failure of the cortical granules to prevent dispermic penetration. Classically a partial hydatidiform mole is triploid. Partial hydatidiform mole appears to be the result of what happens when this cortical granule process fails and an egg can be penetrated by multiple sperm ( Figure 6.5.5). In most women with FRHM, mutations in NLRP7 give rise to recurrent BiCHM with pathology and imprinting defects similar to the common androgenetic CHM.įigure 6.5.5. This group includes a small number of women who have an autosomal recessive condition, familial recurrent hydatidiform mole (FRHM) that predisposes to molar pregnancies. Following both PHM and CHM, there is an increased risk of further HM in subsequent pregnancies: around 2% after a single HM rising significantly to around 15% after two molar pregnancies. Both PHM and CHM are characterized by the presence of two paternal chromosome complements and overexpression of paternally derived genes. Unusual variants are also reported including pregnancies in which a HM coexists with a normal twin, mosaics in which the placenta is partly molar, and diploid biparental complete hydatidiform moles (BiCHMs) that are associated with a familial predisposition to molar pregnancies. CHMs are predominantly androgenetic diploid conceptions, while PHMs are predominantly dispermic triploid conceptions. ![]() Approximately 15% of women with a complete hydatidiform mole (CHM) and 0.5% with a partial hydatidiform mole (PHM) will subsequently require chemotherapy for persistent gestational trophoblastic neoplasia. Hydatidiform moles (HMs) are genetically abnormal conceptions characterized by abnormal chorionic villi, trophoblastic hyperplasia, poor fetal development, and an increased risk of malignant disease development. Sebire, in Brenner's Encyclopedia of Genetics (Second Edition), 2013 Abstract ![]()
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