This patient’s presentation is consistent with a partial hydatidiform mole. Partial hydatidiform moles are characterized by the appearance of sections of normal fetal tissue and normal chorionic villi intermixed with trophoblastic proliferation, symptoms of vaginal bleeding and abdominal pain, and a triploid 69 XXX or 69 XXY karyotype.
Partial moles can be differentiated from complete hydatidiform moles in that complete moles lack any fetal tissue and exhibit diffuse trophoblastic proliferation. Complete moles are also associated with higher levels of Beta-hCG as well as an increased risk of malignant trophoblastic disease (ex. choriocarcinoma) in comparison to partial moles. Additionally, unlike partial moles, complete moles are associated with a 46 XX or 46 XY karyotype, with both sets of chromosomes of paternal origin.
Deutchman reviews the diagnosis of pregnancy problems such as a hydatidiform mole. Ultrasound testing and quantitative beta-hCG and progesterone in the first trimester facilitate early diagnosis of pregnancy-related problems and when used methodically, can determine if a pregnancy is normal, if a miscarriage is present, if a missed abortion has occurred, if an ectopic pregnancy is present or if a hydatidiform mole is present.
Lurain discusses the differences between complete and partial hydatidiform moles. Nearly 90% of complete moles occur in an egg with maternal chromosomes absent or inactive, that has been fertilized by a haploid sperm that undergoes duplication and is 46, XX. On the other hand, most partial moles result from a normal ovum being fertilized by 2 sperm, and result in triploid 69, XXY (or less commonly 69, XXX).
Image A depicts the ultrasound appearance of a partial hydatidiform mole; note the presence of both fetal tissue (left) as well as the characteristic snowstorm appearance (right) in different sections of the image.
Image B demonstrates the trophoblastic proliferation that can be associated with both partial and complete moles.
Illustration A delineates the key differences between partial and complete hydatidiform moles.
Answer 1: This karyotype is not consistent with the triploid karyotype of a partial hydatidiform mole.
Answer 2: This karyotype is consistent with a complete hydatidiform mole, which is described above
Answer 4: This is the karyotype of Klinefelter’s syndrome.
Answer 5: This is the karyotype of Turner’s syndrome.
Deutchman M. Advances in the diagnosis of first-trimester pregnancy problems. Am Fam Physician. 1991 Nov;44(5 Suppl):15S-30S.
PMID:1950980 (Link to Abstract)
Lurain JR. Gestational trophoblastic disease I: epidemiology, pathology, clinical presentation and diagnosis of gestational trophoblastic disease, and management of hydatidiform mole. Am J Obstet Gynecol. 2010 Dec;203(6):531-9. Epub 2010 Aug 21.
PMID:20728069 (Link to Abstract)
USMLE World Step 1 QBank Question #792. Copyright © USMLEWorld, LLC 2012