Ataxia Telangiectasia
Ataxia-telangiectasia (AT) (Boder-Sedgwick syndrom or Louis-Bar syndrome) is a primary immunodeficiency disorder that occurs in an estimated incidence of 1 in 40,000 to 1 in 300,000 births (Lederman, 2000).
Definition/Criteria
AT is characterised by:
Early-onset progressive cerebellar ataxia
Oculo-cutaneous telangiectasia (dilated blood vessels in the eyes and skin)
Immunodeficiency mostly thorough lowering of IgA, IgG and IgE levels.
Chromosomal instability
Hyper sensitivity to ionising radiation
Increased incidence of malignancies primarily lymphoid.
Raised alpha-fetoprotein levels.
Classification
So far there appear to be three forms of AT:
Pure AT where patients present with all/most of the diagnostic symptoms.
Attenuated AT where sufferers do not possess all of the diagnostic symptoms.
Carrier AT where individuals with a single ATM mutation show an increased risk of cancer (known since the 1970’s).
These are sometimes classified into ‘types’ from I to IV.
Type I is the classic syndrome with all manifestations.
Type II lacks some of the typical findings but shows radiosensitivity.
Type III has the classic clinical findings but is not radiosensitive.
Type IV shows only some clinical features and is not radiosensitive.