What is the recurrence risk for holoprosencephaly when there is one affected first-degree relative?

The recurrence risk for holoprosencephaly, particularly when there is one affected first-degree relative, is typically estimated to be around 5%. This estimation is based on the understanding of the genetic components associated with holoprosencephaly, a condition often linked to disruptions in early embryonic development, especially during the formation of the forebrain.

In families with a known case of holoprosencephaly, the presence of a first-degree relative (such as a parent or sibling) who is affected raises the likelihood of recurrence due to possible shared genetic or environmental factors. While exact probabilities can vary based on specific familial contexts and the underlying etiology of the condition (such as chromosomal abnormalities or teratogenic exposures), the general consensus for recurrence when one close relative is affected is usually cited as approximately 5%. This figure reflects a calculated risk that is considered in genetic counseling settings, assisting families in understanding the potential implications for future pregnancies.

Overall, understanding these recurrence risks is crucial for genetic counselors as it guides them in providing informed risk assessments to families affected by genetic conditions like holoprosencephaly.