Ataxia-telangiectasia variant (ATV) is a rare genetic disorder that is characterized by a combination of neurological and immunological symptoms. It is caused by a mutation in the ATM gene, which is responsible for the production of a protein that helps to regulate cell division and repair damaged DNA. Symptoms of ATV include ataxia (lack of muscle coordination), telangiectasia (dilated blood vessels), and immunodeficiency (weakened immune system). Other symptoms may include developmental delays, seizures, and an increased risk of certain types of cancer. Treatment for ATV is supportive and may include physical therapy, speech therapy, and medications to help manage symptoms.