Ataxia-telangiectasia (A-T) is an autosomal recessive chromosome breakage
disorder caused by mutations in the ATM gene. Typically it
presents in early childhood with progressive cerebellar dysfunction along with
immunodeficiency and oculocutaneous telangiectasia. An increased risk of
malignancy is also associated with the syndrome and, rarely, may be the
presenting feature in small children. We describe a 17-year-old boy with slurred
speech, mild motor delays and learning disability diagnosed with atypical A-T in
the setting of T-cell acute lymphoblastic leukemia. Suspicion for A-T was raised
after review of a peripheral blood karyotype demonstrating rearrangements
involving chromosomes 7 and/or 14. The diagnosis was confirmed after molecular
testing identified a novel homozygous missense variant in ATM
(c.5585T>A; p.Leu1862His) that resulted in protein instability and
abolished serine/threonine protein kinase activity. To our knowledge, this is
the first report of concurrent A-T and lymphoid malignancy diagnoses in an older
child or adult with only mild neurological disease. Our experience suggests that
screening for the disorder should be considered in any individual with lymphoid
malignancy and neurological findings, especially as radiation and certain
chemotherapy protocols are contraindicated in A-T.
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