Ataxia-telangiectasia results from biallelic pathogenic variants in ATM (chromosome 11). ClinGen has classified the ATM–ataxia-telangiectasia gene-disease relationship as DEFINITIVE. The condition follows autosomal recessive inheritance. ATM encodes a kinase central to coordinating cellular responses to DNA double-strand breaks; loss of ATM function disrupts DNA repair pathway activation, cell cycle checkpoint signaling, and apoptotic regulation. These molecular deficits underlie the characteristic combination of progressive cerebellar neurodegeneration, combined immunodeficiency, genomic instability, and elevated susceptibility to malignancy—particularly lymphoid tumors—that define the clinical syndrome. One recognized subtype is described in the packet: ataxia-telangiectasia with generalized skin pigmentation and early death.

GeneReviews states that no consensus clinical diagnostic criteria for A-T have been published. Two scenarios may prompt diagnostic consideration: detection of reduced T-cell receptor excision circle (TREC) levels through newborn screening for severe combined immunodeficiency (SCID), and presentation of characteristic clinical features in a symptomatic individual. GeneReviews notes that newborns with classic A-T may demonstrate reduced TREC levels, providing a potential early detection pathway through SCID newborn screening programs. Confirmatory evaluation typically involves molecular genetic testing of ATM and assessment of ATM protein expression or kinase function. Elevated serum alpha-fetoprotein is an obligate biochemical finding documented in the packet. GeneReviews describes post-diagnosis evaluation as encompassing neurologic assessment, immunologic workup, and pulmonary function evaluation across both classic and variant phenotypes.

No drugs with active FDA-approved market status for A-T are documented in this packet. GeneReviews management documentation notes that guidelines for A-T are largely expert- and evidence-based, reflecting the limited availability of clinical trial data specific to this condition. Multiple agents carry FDA orphan drug designation for A-T: betamethasone (Acasti Pharma), dexamethasone sodium phosphate encapsulated in autologous erythrocytes (Quince Therapeutics), N-acetyl-leucine (IntraBio), and nicotinamide riboside chloride (ChromaDex)—all with DESIGNATED status and without FDA approval for this indication. GeneReviews management guidance describes a multidisciplinary care framework addressing neurologic, immunologic, and respiratory domains. Surveillance documented in GeneReviews encompasses monitoring of immunologic function, pulmonary status, and cancer-related assessment. Management of recurrent sinopulmonary infections, which are a primary driver of morbidity, is a focus of documented clinical protocols.

GeneReviews describes classic A-T as following a course of progressive neurologic deterioration; most individuals with classic A-T progress to wheelchair dependence during the second decade of life. Pulmonary complications arising from recurrent infections and malignancy—particularly lymphoid tumors—are primary contributors to morbidity and mortality in this population. Life expectancy is reduced in classic A-T, though GeneReviews notes that respiratory management and oncologic surveillance have influenced outcomes in some populations. Variant A-T is associated with slower neurologic progression and longer life expectancy, with GeneReviews acknowledging substantial inter- and intrafamilial variation across the A-T phenotypic spectrum.

Active clinical investigations specific to A-T documented in this packet include: NCT07215416, a Phase 1 trial of mutation-targeted precision genetic therapy for A-T, sponsored by Timothy Yu (recruiting as of August 2026; estimated completion December 2036); and NCT07709728, a biomarker characterization study for babies and young children with A-T, conducted by the University of Nottingham (not yet recruiting; start estimated September 2026). GeneReviews notes that most management guidelines reflect expert consensus given the limited clinical trial landscape for A-T. The A-T Children's Project patient advocacy organization is referenced in GeneReviews as an active resource for affected families in this disease community.