Which of the following is the chromosomal composition of the complete mole?
## Core Concept
A complete mole, also known as a complete hydatidiform mole, is a type of gestational trophoblastic disease characterized by the abnormal development of placental tissue. It typically results from an empty egg that has lost its chromosomes being fertilized by one or two sperm. The chromosomal composition of a complete mole usually involves an entirely paternally derived genome.
## Why the Correct Answer is Right
The correct chromosomal composition of a complete mole is **46,XX**, which usually arises when an egg that has lost its chromosomes (nullisomic) is fertilized by a single sperm that then duplicates its chromosomes (endoreduplication) or by dispermy (two sperm) where one sperm is inactivated. This results in a completely paternally derived genome without any maternal DNA contribution. The presence of only paternal chromosomes leads to the abnormal proliferation of trophoblastic tissue.
## Why Each Wrong Option is Incorrect
- **Option A:** is incorrect because this represents a normal female karyotype, which includes both maternal and paternal chromosomes in a balanced diploid state.
- **Option B:** is incorrect because this karyotype represents a normal male karyotype, which, although diploid, includes both X and Y chromosomes and does not account for the exclusively paternal origin of a complete mole.
- **Option D:** is incorrect because this represents a triploid state, often seen in partial moles where there is an extra set of chromosomes, usually resulting from dispermy.
## Clinical Pearl / High-Yield Fact
A key clinical pearl is that complete moles have a higher risk of progressing to gestational trophoblastic neoplasia compared to partial moles. The risk of malignancy is higher with complete moles, which is why close follow-up with serial beta-hCG levels is crucial after evacuation.
## Correct Answer: . 46,XX