A 7-year-old boy has progressive truncal ataxia, oculocutaneous telangiectases over the bulbar conjunctivae and ears, recurrent sinopulmonary infections, and elevated alpha-fetoprotein. Immunoglobulin profile shows low IgA and IgG2. The gene mutated in this condition encodes:
- A A serine-threonine kinase activated by DNA double-strand breaks ✓
- B A DNA helicase of the RecQ family
- C A nucleotide excision repair endonuclease
- D A mismatch repair protein
Correct answer: A. A serine-threonine kinase activated by DNA double-strand breaks
Explanation
Ataxia-telangiectasia is autosomal recessive, caused by ATM mutations. ATM is a serine-threonine kinase recruited to double-strand DNA breaks, so defective signalling produces chromosomal instability, radiosensitivity and lymphoreticular malignancy risk. Telangiectases appear on conjunctivae and sun-exposed skin, and selective IgA and IgG2 deficiency drives sinopulmonary infections. RecQ helicase defects cause Bloom and Rothmund-Thomson syndromes, and NER defects cause xeroderma pigmentosum, all clinically distinct here.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.