Sex-linked disorders, also known as X-linked diseases, refer to defects in the X chromosome that are inherited and cause certain diseases. According to MedlinePlus, X-linked diseases typically are most severe in males as they only have one X chromosome while females have two X chromosomes.

Sickle cell disease, also called sickle cell anemia, is the most common worldwide disease that is passed through families, according to University of Iowa Health Care, or UIHC. Individuals with sickle cell anemia may suffer from painful episodes that can occur suddenly and last for days.

Avascular necrosis, also known as osteonecrosis or asceptic necrosis, is defined as bone death due to loss of blood supply to the affected area. It can be caused by long-term use of steroids, excessive alcohol consumption and illnesses such as sickle cell anemia.

Sickle cell disease is a blood disorder affecting approximately 100,000 people in the United States, most of them African-American. It is a complicated disease, and according to a February 2015 study in "Anemia," even some family physicians find it difficult to manage.