Combined immune deficiencies (CID) are a group of primary immunodeficiencies in which both T cells and B cells of the adaptive immune system are either low or function poorly.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder that causes neurological symptoms (like unsteady gait), dilated corkscrew-shaped blood vessels in the white of the eyes and on sun-exposed skin, combined immune deficiency, and high risk of cancer.