Case Report: Ataxia telangiectasia with severe hemorrhagic cystitis

Background Ataxia telangiectasia (AT) is a rare autosomal recessive genetic disorder caused by variants in the ataxia-telangiectasia mutated (ATM) gene. AT is characterized by progressive cerebellar degeneration, telangiectasia, immunodeficiency, cancer susceptibility, and radiosensitivity. This report presents a case of classic AT complicated by severe hemorrhagic cystitis, a rare clinical manifestation. Genetic analysis revealed novel variants in the ATM gene. Case presentation A 12-year-old Han Chinese boy presented with recurrent gross hematuria that progressed in frequency and severity after completion of chemotherapy for T-cell acute lymphoblastic leukemia (ALL). He had developed gait instability at age 2, and brain MRI showed cerebellar atrophy. Genetic testing revealed compound heterozygous ATM variants: c. 8357GT (p. Gly2786Val) (maternal) and IVS54+3AC (paternal) (NM₀00051). Cystoscopy revealed multiple telangiectatic lesions of the bladder mucosa with associated yellow-brown sedimentation. Emergency cystoscopic electrocoagulation controlled the bleeding. Conclusion We report two novel ATM variants (c. 8357GT, IVS54+3AC) in a patient with classic AT who developed severe hemorrhagic cystitis associated with bladder wall telangiectasia. AT patients may be at risk for delayed, potentially life-threatening hemorrhagic cystitis, particularly following cyclophosphamide exposure. Cystoscopy is essential for diagnosis and enables timely endoscopic management.