Tuesday, November 6, 2018

Repeated USMLE Questions Step 1- 236






An 18 year-old man presents to the office for evaluation of multiple swellings in his neck. On examination, he has multiple large lymph nodes in his neck. Neurological examination reveals poor coordination on walking. Biopsy of lymph node is positive for lymphoma. He is diagnosed with ataxia-telangiectasia.

What is the etiology of this disorder?

A- Defective DNA repair mechanisms

B- Deletion of VHL gene on chromosome 3

C- Mutation in the NF1 gene on chromosome 17

D- Mutation in PKD1 on chromosome 16

E- Mutation in APC gene on chromosome 5

Answer






Ataxia-telangiectasia is a recessive autosomal disorder caused by defective DNA repair mechanisms. It results in weakness of immune systems which leads to multiple infections and increasing risk of cancer.

The correct answer is A