#ExistInterpData>Background information for Molar Pregnancy, 16 DNA Markers:
Characteristics of Complete Mole: Typically presents with vaginal bleeding and ultrasound showing enlarged placenta, marked trophoblastic hyperplasia and swollen villi. If diagnosed in the first trimester, embryonic tissue may be present; by the second trimester, no fetal tissue is evident.
Characteristics of Partial Mole: Typically presents as a threatened or missed abortion at the end of the first trimester; if still viable in the second trimester, a large placenta with hydropic change of some villi and a growth restricted fetus is usually observed.
Incidence of Complete and Partial Moles: Approximately 1 in 1500 and 1 in 700 pregnancies respectively, with regional and ethnic variation observed.
Inheritance: The majority of cases are de novo; rare recurrences may be due to heritable mutations.
Cause of Complete Mole: Typically due to doubling of chromosome content of a normal 23,X sperm fertilizing an egg lacking a maternal set of chromosomes; occasionally results from two sperm fertilizing an egg lacking maternal chromosomes; karyotype is 46,N.
Cause of Partial Mole: Typically due to a normal ovum fertilized by two sperm resulting in a 69,XXX or 69,XXY chromosome complement.
Clinical Sensitivity: Estimated to be 99 percent.
Clinical Specificity: Complete mole: greater than 99 percent; partial mole: estimated to be 50-60 percent.
Methodology: PCR followed by capillary electrophoresis. Specimens are analyzed using 15 short tandem repeat (STR) markers (D8S1179, D21S11, D7S820, CSF1PO, D3S1358, TH01, D13S317, D16S539, D2S1338, D19S433, vWa, TPOX, D18S51, D5S818 and FGA) and one gender marker (amelogenin).
Analytical sensitivity and specificity: 99 percent.
Limitations: Contamination of villi / decidua may occur. Inhibitors present in the specimen can interfere with the polymerase chain reaction. Rare case of heritable molar pregnancy may appear normal by STR analysis.
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