Ataxia-Telangiectasia (A-T) is a neurodegenerative disease caused by bi-allelic mutations in the Ataxia-Telangiectasia-Mutated (ATM) gene. Complete lack of ATM activity leads to severe A-T and mutations allowing for residual activity cause a milder phenotype, termed variant A-T. There are only sparse data on the variability in phenotypes of variant A-T patients carrying the same mutations. A retrospective study of 15 patients with variant A-T, all double homozygous for the same mutations was conducted. The age of first symptom ranged from 4-180 months, including: truncal ataxia at <18 months of age in 9 patients, ataxia and instability only during fever in one patient, dystonia in one patient and malignancy in 4 patients. Global developmental delay and occulo-motor apraxia were recorded in 4/14 patients. Variant A-T patients with the same mutations in ATM, have variable phenotypes. Environmental, epigenetic, and post translational factors are likely to play a role in creation of the phenotype in variant A-T patients.

共济失调-毛细血管扩张（AT）是一种神经退行性疾病，由共济失调-毛细血管扩张-突变（ATM）基因中的双等位基因突变引起。完全缺乏ATM活性会导致严重的AT，而允许残留活性的突变会引起较轻的表型，称为变体AT。关于携带相同突变的变异AT患者的表型变异性，只有很少的数据。进行了一项回顾性研究，对15例AT变体患者进行了相同突变的双重纯合。首次症状的年龄范围为4-180个月，其中包括：9例患者<18个月时出现截短性共济失调；仅一名患者发烧时出现共济失调和不稳定；一名患者出现肌张力障碍； 4例发生恶性肿瘤。在4/14例患者中记录了总体发育迟缓和眼球运动失用。在ATM中具有相同突变的变异AT患者具有可变的表型。环境，表观遗传因素和翻译后因素可能在变异型AT患者的表型产生中发挥作用。