Hoyeraal Hreidarsson syndrome (HHS) is a rare disorder that is passed down from parents to children. This disorder is passed down through the X chromosome in a recessive manner. Females have two X chromosomes, while males have one X and one Y chromosome. Hoyeraal Hreidarsson syndrome is more common in males because they have only one X chromosome. They do not have a second X chromosome with a functioning gene like females do. Females are carriers and usually do not show symptoms.
Hoyeraal Hreidarsson syndrome is found at infancy. Symptoms of Hoyeraal Hreidarsson syndrome include poor growth of the child during pregnancy, head size that is smaller than expected (microcephaly), the back of the brain is not fully formed (cerebellar hypoplasia), a poor immune system, failure of bone marrow (aplastic anemia), and a higher chance of getting cancer.
Hoyeraal Hreidarsson syndrome can be detected before the baby is born through an ultrasound. If Hoyeraal Hreidarsson syndrome is known to occur in other family members, genetic testing can be done before birth as well. Treatment can include bone marrow transplants and careful attention to sickness or infections. If you or a family member has been diagnosed with Hoyeraal Hreidarsson syndrome, talk with your doctor about the most current treatment options as well as signs that you may need immediate medical attention.