What is Wiskott-Aldrich syndrome (WAS), and what does it have to do with my child’s immune system?
WAS is a rare genetic immunodeficiency that keeps a child's immune system from functioning properly. It also makes it difficult for a child's bone marrow to produce platelets, making a child prone to bleeding. According the National Institutes of Health, only 1 to 10 out of every 1 million boys has WAS.
The human immune system constantly patrols, protects and defends the body from all types of “enemies,” including:
The blood and immune system arises from a developing fetus’ bone marrow. Bone marrow stem cells eventually mature into all of the different blood cells, including platelets that control bleeding, and two immune cell types that play the important roles in warding off infection: T cells (white blood cells that identify and attack perceived “invaders”) and B cells (white blood cells that produce antibodies against infection). In addition, stem cells give rise to other types of white blood cells (neutrophils, macrophages, natural killer cells) that also play important roles in clearing infections.
When a child has Wiskott-Aldrich syndrome:
- the T cells and B cells are there but don’t work right
- his white blood cells do not properly reach the sites of infections
Without normal immune cells, a child with WAS is at constant risk for:
- eczema (atopic dermatitis)
- chronic, bloody diarrhea
- ear and sinus infections
- viral infections like herpes, cytomegalovirus (CMV) and Epstein-Barr virus (EBV)
- many other types of infection
These problems are further complicated by the other aspect of WAS: The child’s body does not properly produce platelets, the clotting agents that stop bleeding from getting out of control. The platelets that are produced are small and are only produced in small numbers. Without healthy platelets, the child is likely to experience frequent and hard-to-control bleeding, even from the mildest bumps and scrapes. This bleeding can occur:
- under the skin
- from the nose
- from the gums and mouth
- in bowel movements
- in the brain
As a result of these combined deficiencies, children with WAS are also at elevated risk for developing:
There is more than one kind of WAS. The majority of boys with WAS have the type known as the “classic” form, though some experience a milder form of the disease known as X-linked thrombocytopenia (XLT). This is caused by a defect in the same gene involved in classic WAS, but the symptoms are much milder.
Usually, children with X-linked thrombocytopenia have platelets that are overly small in both size and number. As a result, they have trouble with easy bleeding and bruising, but do not experience the other, more severe complications.
However, it is often difficult to predict whether a male baby born with a mutation in the WAS gene will develop the severe form of the disease (WAS) or its milder variant, XLT. Moreover, also patients with XLT can progress to develop typical complications of WAS as they become older. Therefore, it is important that both patients with WAS and those with XLT be followed regularly by their doctor and by specialists in this disease.
Your treating clinician can give you specifics about the form of WAS your child has.
Is Wiskott-Aldrich syndrome treatable?
The only proven treatment for Wiskott-Aldrich syndrome is a stem cell transplant (using bone marrow, peripheral blood or umbilical cord blood from a healthy, suitably matched donor). Because stem cells have the special ability to develop into other types of cells, a transplant can give the child’s body an essential new source of healthy white blood cells – rebuilding his immune system and allowing him to successfully ward off infections.
Although WAS is a potentially life-threatening disease, there is hope: a timely diagnosis and prompt treatment make the condition very treatable in the vast majority of cases. You and your child are in the best possible hands.
What causes Wiskott-Aldrich syndrome?
WAS is a genetic disorder – meaning it is caused by a mutation, or error, in the child’s genes.
Every living organism on this planet is made up of genes – tiny, complex coded instructions that determine what we look like, who we’re related to and how we’ll pass on our traits to our children (and our children’s children). Sometimes, the genes we inherit from a parent also contain mutations, or mistakes in the genetic code.
When the mutation happens on the X chromosome – one of the two chromosomes, X and Y, that determine a person’s gender – it can be passed on by mothers to their sons. Because the mothers have two X chromosomes, even if they have a mutation on one of the two X chromosomes, they still have a normal copy of the gene on the other X chromosome, and therefore they themselves don’t experience any physical problems from the mutation. However they can transmit the X chromosome with the mutation – and the disease it causes – over to their male children. Boys have only one X chromosome, so male babies who inherit from their mother the faulty X chromosome with, will have the disease. Sometimes a boy can be born with the faulty X chromosome, even though his mother is not a carrier of the mutation (in this case, the mutation arises in the germ cell of the mother).
WAS develops as the result of a defect in a gene located on the X chromosome. Because females have two X chromosomes, but males have only one, women who carry a defect of the WAS gene in one of their X chromosomes do not develop symptoms of the disease (because they have a “healthy” X chromosome), but can pass the defective gene on to their male children. As a result, WAS almost always affects boys only.
Signs and symptoms
What are the symptoms of Wiskott-Aldrich syndrome?
Nearly every child with WAS will start showing symptoms as a baby, between the time he’s born and the time he turns 1. The symptoms usually include:
- frequent and easy bleeding that can occur:
- from the nose
- from the mouth and gums
- in bowel movements
- frequent and easy bruising
- a small red rash consisting of “dots” under the skin (these are called petechiae)
- chronic infections
- eczema (atopic dermatitis)
- autoimmunity (anemia, arthritis, inflammatory bowel disease, nephritis, vasculitis)
Since WAS is a genetic disorder (caused by an error in the genes), it is always present at birth. (Symptoms may not show up until later in his infancy, however.)