Recurrent hydatidiform mole
Recurrent hydatidiform mole is a condition characterized by the occurrence of at least two abnormal pregnancies resulting in the formation of a mass of cells from an abnormally developed embryo and placenta.
Overview
A hydatidiform mole is a mass that forms early in pregnancy. While a sporadic mole occurs once, the recurrent form involves multiple occurrences. The first symptom is often vaginal bleeding in the first trimester. These moles must be surgically removed, as they do not discharge naturally. There is a risk that remaining tissue can become a persistent mole or an invasive mole, and in rare cases, it can transform into a cancer called gestational choriocarcinoma.
Causes
Mutations in the NLRP7 and KHDC3L genes are the primary causes of this condition. These genes are critical for normal egg cell (oocyte) development and are thought to play a role in genomic imprinting—a process where certain genes are turned off based on which parent they were inherited from. Mutations lead to impaired protein function, resulting in abnormal oocytes that cannot develop into a healthy pregnancy.
Rarely, mutations in genes involved in the production of oocytes and sperm cells—specifically those involved in the exchange of genetic material during cell division—can also cause the condition. These mutations result in oocytes that lack chromosomes, leading to an embryo that cannot develop normally.
Genes Associated with Recurrent hydatidiform mole
- KHDC3L
- NLRP7
Inheritance
Recurrent hydatidiform mole is inherited in an autosomal recessive pattern, meaning both copies of the gene in each cell must have mutations for the condition to occur. Parents of an affected individual typically carry one copy of the mutated gene but do not show symptoms themselves.