Individuals who have the disease have a mutated WAS (Wiskott-Aldrich syndrome) gene, which codes for the protein named Wiskott-Aldrich Syndrome Protein (WASP). This protein is present in leukocytes (white blood cells that fight against infection), as well as platelets. Consequently, individuals who are diagnosed with WAS are more susceptible to infections and bleeding.

The disease is inherited as an X-linked recessive trait. Therefore, it affects males almost exclusively. If a male inherits the mutated WAS gene, he will develop the disease because he has only one X chromosome.

Females, on the other hand, have two X chromosomes. Even if a female inherits the mutated gene, chances are the other gene will be healthy because the disease is extremely rare. The female would need to inherit two mutated X chromosomes in order to develop the disease. However, if the female inherits one mutated gene she is a carrier for the disease, and there is a 50% chance she will pass the gene to each of her children. Carriers do not express symptoms of the disease.

WAS symptoms range from mild to severe and begin early in childhood. A less severe form of the disease will mainly affect the platelets. Common symptoms include eczema, thrombocytopenia, immune deficiency and bloody diarrhea.

Individuals who have WAS are more susceptible to bleeding and infections, as well as malignancies like lymphoma or leukemia. Common infections include otitis media (ear infections), sinusitis, pneumonia, herpes simplex and the Epstein-Barr virus (EBV). In addition, WAS patients frequently suffer from autoimmune disorders like vasculitis (inflamed blood vessels), arthritis and autoimmune hemolytic anemia.

About 81% of individuals with WAS develop eczema, a skin disorder that causes red itchy patches of skin on the face, elbows, knees and arms. Eczema usually improves as the patient ages. However, in some cases, persistent eczema and skin rashes may cause secondary infections. Other complications may include cellulitis (inflamed connective tissue), abscesses or erythroderma (reddening of the skin).

WAS is diagnosed when the mutated gene is identified. Some individuals may experience physical symptoms and a blood test may detect thrombocytopenia. Gene testing is also available for possible carriers of the disease and for fetuses.

Amniocentesis: Amniocentesis may be performed to detect genetic abnormalities in the fetus. This procedure is performed at about 15-18 weeks gestation. During the procedure a long, thin needle is inserted into the pregnant woman's abdominal wall to the uterus. A small amount of fluid is removed from the sac surrounding the fetus. The fluid is then analyzed for genetic abnormalities. There is a slight risk of infection or injury to the fetus, and a chance of miscarriage.

CBC: A complete blood count (CBC) test is usually conducted to determine how many and what types of cells are in the blood. Patients who have WAS will have a low platelet count and weak immune response. Healthy individuals have anywhere from 150,000 to 450,000 platelets per microliter of circulating blood in the body. The risk of bleeding increases as the number of platelets decreases. When there are less than 10,000 platelets per microliter of circulating blood, the condition is considered severe, and internal bleeding may occur.

Chorionic villus sampling: During chronionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the uterus during early pregnancy to screen the fetus for genetic defects. Depending on where the placenta is located, CVS can be performed through the cervix (transcervical) or through the abdomen (transabdominal). The risks of infections or fetal damage are slightly higher than the risks of amniocentesis. Fetal loss occurs about two percent of the time.

DNA test: The DNA from a sample of blood can be analyzed for a mutation in the WAS gene. This test can confirm a diagnosis and will also help the healthcare provider predict how severe the form of the disease will be. In addition, if the specific WAS gene mutation is identified in an affected child, that child's mother can be tested to confirm that she is a carrier.