WAS Facts

WAS Facts

Wiskott-Aldrich Syndrome (WAS) is a serious medical condition that causes problems both with the immune system and with blood clotting. The immune abnormalities cause WAS patients to be very susceptible to infections with bacterial, fungal, and viral organisms. 

The problems with easy bruising and bleeding in WAS patients result from having low numbers of small, non-functional platelets, the cells in the blood that clump together to form blood clots. 

WAS is an X-linked recessive disease meaning that females may carry the gene for the disorder but don’t develop symptoms whereas boys develop the clinical problems associated with the disease.  WAS is estimated to occur in approximately 1 out of every 100,000 boys.1  Milder forms of WAS in which patients have the blood clotting problems but have only mild immune abnormalities may also occur and are typically referred to by the name of X-Linked Thrombocytopenia (XLT). 


Children with WAS are diagnosed most commonly in the first year of life because of easy bruising, abnormal bleeding, or low platelet counts.  Patients may also have severe or frequent infections including:

  • Bacterial ear infections, sinus infections, pneumonia, or blood infections.
  • Severe viral infections with viruses including Varicella or Herpes Simplex virus. 
  • Pneumocystis jiroveci, which is carried in the airway of most normal individuals but can cause a fatal pneumonia if not diagnosed and treated appropriately in WAS patients.

Patients with WAS may also have other symptoms that can provide clues to the diagnosis including:

  • Rash – most commonly a severe eczema-like rash.  
  • Autoimmunity – patients with WAS may develop a variety of autoimmune problems.  The most common of these is autoimmune attack of the red blood cells (Autoimmune Hemolytic Anemia) or platelets (Idiopathic Thrombocytopenic Purpura) but patients may also develop arthritis or inflammation of blood vessels (vasculitis).  
  • Malignancies – patients with WAS are at high risk of developing cancer, particularly lymphomas.  These may occur in childhood but develop most commonly in teenagers or young adults with the disease.   


The most helpful clues that a patient may have Wiskott-Aldrich Syndrome are the symptoms of bleeding and easy bruising combined with frequent infections and a rash that looks like eczema.  The following tests can be helpful in making a definitive diagnosis in a patient suspected of having WAS:

  • Complete Blood Counts (CBC with differential) – Platelet counts are usually very low compared to normal individuals and platelet size is very small (less than 6 femtoliters). Patient may also have anemia.
  • T cell, B cell, and NK cell counts – T, B, and NK cells are different types of lymphocytes that play various roles in the immune response.  Numbers of these cells may be low or normal in patients with WAS.
  • Functional testing of T lymphocytes – T lymphocytes from WAS patients often do not function well to protect against infections. These cells can be tested in the lab to determine if they grow and divide normally when they are challenged.
  • Immunoglobulin levels (IgG, IgM, IgA, IgE) – Immunoglobulin levels may be artificially normal during the first 3-4 months of life because of antibody that crosses the placenta from the mother during pregnancy.  Over time, antibody levels (particularly IgG) tend to fall in patients with WAS. In addition, patients often do not make normal antibodies to immunizations or infections so testing to measure antibody responses to specific vaccines like tetanus or polysaccharides usually shows abnormally low levels. If low, these can be replaced in the patient by giving Intravenous Immune Globulin (IVIG).
  • Specific genetic testing - gene sequencing to identify mutations in the WASP gene which is defective in patients with Wiskott-Aldrich Syndrome can confirm a diagnosis of WAS. 

Immunology Diagnostic Laboratory (IDL) at Seattle Children’s

Immunology Diagnostic Laboratory offers genetic and other testing for Wiskott-Aldrich Syndrome and an array of other primary immune deficiencies and has extensive expertise in evaluating patients with WAS and other disorders. Our doctors are available to assist physicians, patients, and family members with questions about diagnosis and treatment.