Mutations at the ataxia-telangiectasia locus cause a distinctive autosomal recessive syndrome in homozygotes and predispose heterozygotes to cancer and ischemic heart disease.

To examine mortality rates among persons carrying a mutated ataxia-telangiectasia gene.

Retrospective cohort study.

The United States and Canada.

405 grandparents of patients with ataxia-telangiectasia.

Ages at death and risk for death (from all causes, cancer, ischemic heart disease, and other causes) among carriers and noncarriers of ataxia-telangiectasia mutations.

Compared with noncarriers, carriers of a mutated ataxia-telangiectasia allele had a significantly increased risk for death at 20 through 79 years of age (relative risk, 1.9 [95% CI, 1.3 to 2.8]) (P < 0.001). On average, carriers died 7 to 8 years earlier than noncarriers. Cancer caused most of the excess deaths, and ischemic heart disease caused the remainder. Among carriers, relative risk for death from cancer and ischemic heart disease before 80 years of age was 2.6 (CI, 1.4 to 4.7; P = 0.002) and 2.0 (CI, 1.0 to 4.0; P = 0.062), respectively. Compared with noncarriers, carriers who died of cancer were a mean of 4 years younger (P > 0.2) and carriers who died of ischemic heart disease were a mean of 11 years younger (P = 0.006).

Carriers of mutations at the ataxia-telangiectasia locus, who make up 1.4% to 2% of the general population, have a higher mortality rate and an earlier age at death from cancer and ischemic heart disease than noncarriers.