WAS patients have increased susceptibility to infections, particularly of the ears and sinuses, and this immune deficiency has been linked to decreased antibody production and the inability of immune T cells to effectively combat infection. Genetics
WAS is associated with mutations in a gene on the short arm of the X chromosome (Xp11.23) that was originally termed the Wiskott-Aldrich syndrome protein gene and is officially known as WAS (Gene ID: 7454). X-linked thrombocytopenia (XLT) is also linked to pathogenic variants in the WAS gene, although some variants tend to be more strongly associated with XLT versus others that are more associated with WAS. The rare disorder X-linked neutropenia has also been linked to a specific subset of WAS mutations.The protein product of WAS is known as WASp. It contains 502 amino acids and is mainly expressed in hematopoietic cells (the cells in the bone marrow that develop into blood cells). The main function of WASp is to activate actin polymerization by serving as a nucleation-promoting factor (NPF) for the Arp2/3 complex, which generates branched actin filaments. Several proteins can serve as NPFs, and it has been observed that in WAS platelets the Arp2/3 complex functions normally, indicating that WASp is not required for its activation in platelets. In T-cells, WASp is important because it is known to be activated via T-cell receptor signaling pathways to induce cortical actin cytoskeleton rearrangements that are responsible for forming the immunological synapse.The severity of the symptoms produced by pathogenic variants in the WAS gene generally correlates with their effects on WASp.
Wiskott–Aldrich syndrome is a condition with variable expressivity, meaning that even within the same family some may exhibit only chronic thrombocytopenia while others experience severe, life-threatening complications of Wiskott–Aldrich syndrome in infancy or childhood. Given symptoms often progress with age, it is challenging to predict how affected a newly diagnosed infant will eventually be. There is some genotype-phenotype correlation, with most individuals with X-linked thrombocytopenia having missense variants in the WAS gene versus 86.5% of those that make no WAS protein having the classic Wiskott–Aldrich syndrome phenotype. Overall the prognosis for individuals with Wiskott–Aldrich syndrome has improved considerably over the past decades due to earlier diagnoses and more access to treatments. Epidemiology
The estimated incidence of Wiskott–Aldrich syndrome in the United States is one in 250,000 live male births. While still a rare disease, this makes it more common than many genetic immunodeficiency syndromes such as hyper-IgM syndrome or SCID, which have an estimated incidence of about one in 1,000,000 live births, and Wiskott–Aldrich syndrome is thought to account for 1.2% of all inherited immunodeficiencies in the United States. WAS occurs worldwide and is not known to be more common in any particular ethnic group. History
The syndrome is named after Dr. Alfred Wiskott (1898–1978), a German pediatrician who first noticed the syndrome in 1937, and Dr. Robert Anderson Aldrich (1917–1998), an American pediatrician who described the disease in a family of Dutch-Americans in 1954. Wiskott described three brothers with a similar disease, whose sisters were unaffected.