The Scenarios of Females Inheriting Hemophilia
As an X-linked recessive trait, hemophilia occurs almost exclusively in males. However, there are circumstances where females can experience bleeding symptoms.
Women with mild hemophilia
In some cases, female carriers of hemophilia can have low levels (<50%) of either factor VIII or factor IX and may experience bleeding symptoms. Female carriers who have bleeding symptoms are considered to have mild hemophilia.
Daughters of a Father with Hemophilia and a Carrier Mother
In some cases, it is possible for a female to have a father with hemophilia and a mother who is a carrier, and thereby inherit an affected X chromosome from both parents. Such daughters would have hemophilia, which may be mild, moderate or severe.
Turner syndrome is a rare chromosomal disorder in which females carry only one X chromosome. If these females inherit the X chromosome that carries the hemophilia gene, they will have hemophilia.
Also once referred to as lyonization, skewed x-inactivation occurs when the affected X with the hemophilia gene is more active than the unaffected X. When this occurs, females can have low factor levels.
Low level carriers reclassified as mild hemophilia
In 2020, the IHTC sent a letter to those patients who had been identified as "low level carriers." These patients are now considered to be diagnosed with mild hemophilia.
Read the letter