A 5-year-old girl has progressive cerebellar ataxia beginning in infancy, oculocutaneous telangiectasias over the bulbar conjunctivae, recurrent sinopulmonary infections, and choreoathetotic movements. Immunoglobulin levels show low IgA and IgG. Which laboratory result would best support the diagnosis?
- A Markedly reduced serum uric acid
- B Low serum ceruloplasmin
- C Markedly elevated serum alpha-fetoprotein ✓
- D Elevated sweat chloride
Correct answer: C. Markedly elevated serum alpha-fetoprotein
Explanation
Ataxia telangiectasia, caused by autosomal recessive ATM mutations, produces progressive cerebellar ataxia, oculomotor apraxia, conjunctival telangiectasias, immunodeficiency with low IgA and IgG subclasses, and chromosomal instability with radiosensitivity. Serum alpha-fetoprotein is characteristically and persistently elevated and serves as a reliable screening marker. Low ceruloplasmin indicates Wilson disease, low uric acid fits Lesch-Nyhan, and raised sweat chloride indicates cystic fibrosis, none of which combine ataxia with telangiectasias.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.