This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics And Genetic Disorders, Subject name: Pediatrics
Defective DNA repair is seen in - 
Select and explain. 
A. Tuberous sclerosis, B. Ataxia telangiectasia, C. Von Hippel Lindau disease, D. Neurofibromatosi 1
B: Ataxia telangiectasia
Answer: B: Ataxia telangiectasia 
Explanation: Ans. is 'b' i.e., Ataxia telangiectasiaAtaxia telangiectasiao Ataxia Telangiectasia (AT) is an autosomal recessive disorder. It is due to mutation of AT gene located on chromosome 11. There is defective DNA repair that results in multiple chromosomal breakso Patients present in first decase of life. Features are : -i) Oculocutaneous telengiectasiaii) Neurological - Ataxia, dysarthria, extensor plantar response, myoclonic jerks, areflexia, distal sensory deficity.iii) Immunodeficeincy-Thymichypoplasiawithcellularandhumoral (IgAandIgG2) immunodeficeincy.iv) Recurrent pulmonary infectionsv) Endocrine disorders- Tye I DMvi) Premature agingvii) Malignancies ? Lymphoma, Hodgkin's disease, acute T cell leukemia, breast cancer.