Proof-of-principle for successful hematopoietic stem cell gene therapy has been provided for patients with Wiskott–Aldrich syndrome. In July 2013 the Italian San Raffaele Telethon Institute for Gene Therapy (HSR-TIGET) reported that three children with Wiskott–Aldrich syndrome showed significant improvement (improved platelet counts, immune functiona, and clinical symptoms) 20–30 months after being treated with a genetically modified lentivirus. In April 2015 results from a follow-up British and French trial six out of seven individuals showed improvement of immune function and clinical symptoms an average of 27 months after treatment with gene therapy. Importantly, neither study showed evidence of leukemic proliferation following treatment, a complication of early attempts at gene therapy using a retroviral vector. It is unknown why these gene therapies did not restore normal platelet numbers, but gene therapy treatment was still associated with transfusion-independence and a significant reduction in bleeding events. A version of this treatment, OTL-103, is being developed by Orchard Therapeutics and (as of 28 June 2021) is undergoing Phase I/II clinical trials. Prognosis
Outcomes from Wiskott–Aldrich syndrome are variable and depend on how severely an individual is affected (the WAS score may be used to assess disease severity). The milder end of the disease spectrum associated with the WAS gene is referred to as X-linked neutropenia or X-linked thrombocytopenia, and the latter is thought to have a normal life expectancy with reports of minimally affected males surviving into their seventh decade without treatment. Traditionally however Wiskott–Aldrich syndrome has been associated with premature death from causes including bleeding, infections, or malignancy.
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.