A 4-year-old Caucasian boy is evaluated for difficulty walking. Past medical history includes frequent respiratory infections. Cultured cells from this patient demonstrate a high rate of radiation-induced genetic mutation. This patient is most likely to experience which of the following?

Question

A 4-year-old Caucasian boy is evaluated for difficulty walking.  Past medical history includes frequent respiratory infections.  Cultured cells from this patient demonstrate a high rate of radiation-induced genetic mutation.  This patient is most likely to experience which of the following?

Quizplus · Accepted Answer

Ataxia-telangiectasia is an autosomal recessive disorder. Cerebellar atrophy leads to the ataxia that occurs in the first years of life. (Oculocutaneous telangiectasia is another manifestation, but is usually delayed. Telangiectasias are abnormal dilatations of capillary vessels.) Patients with ataxia-telangiectasia also have severe immunodeficiency with repeated sinopulmonary infections. The risk of cancer in these patients is increased significantly because of inefficient DNA repair. DNA damage and repair is an ongoing process. A lot of naturally-occurring agents cause DNA damage: sunlight, UV light, ionizing radiation (gamma and X-ray), and free oxygen radicals are produced during the cell cycle. Some chemicals (hydrocarbons in cigarette smoke, aflatoxins produced by moldy peanuts) are also harmful to DNA. DNA repair occurs continuously by means of direct reversal of damage, base and nucleotide excision repair, and mismatch repair. A number of inherited disorders are caused by deficient DNA-repair enzymes: (Choice A) Neurofibrillary tangles in the neocortex are seen in Alzheimer disease. (Choice C) Loss of neurons in the substantia nigra is characteristic of Parkinson disease. (Choice D) Atrophy of caudate nucleus is seen in Huntington disease. (Choice E) Posterior column involvement is seen with both vitamin B 12 deficiency and syphilis. (Choice F) The presence of Lewy bodies is characteristic of Parkinsonism. Educational Objective: Ataxia-telangiectasia is an autosomal-recessive disorder resulting from a defect in DNA-repair genes. The DNA of these patients is hypersensitive to ionizing radiation. Manifestations include cerebellar ataxia, oculocutaneous telangiectasias, repeated sinopulmonary infections, and an increased incidence of malignancy.

A 4-Year-Old Caucasian Boy Is Evaluated for Difficulty Walking