Question of the Day
Study for the USMLE Step 2, daily.
USMLE Step 2 Question of the Day
The parents of a 2-year-old boy mention to his pediatrician during a well-visit that over the past six weeks he has had increasing difficulty walking and maintaining his balance. On further questioning, the parents relate that their son always seems to be sick. On physical exam, the pediatrician notes dilated blood vessels in the eyes and the patient’s parents state that he neither has problems sleeping nor any seasonal allergies. The serum levels of which substance would help establish the diagnosis?
Correct Answer:
Explanation:
The patient has symptoms of ataxia-telangiectasia syndrome. The difficulty maintaining his balance shows ataxia and telangiectasia appears in his eyes. Since IgA, IgG, and IgE levels are decreased, the child is also at risk for an increased frequency of infections. Immunoglobulin levels are depressed because this syndrome results from a deficiency of a tumor suppressor/serine-threonine kinase that links double-stranded breaks in DNA to cell-cycle arrest. Since lymphoid cells have rapid turnover, they will have a high rate of DNA processing errors and so will be more severely affected by a defect in DNA mismatch repair than other cell types with a lower rate of turnover. Alpha-fetoprotein levels are elevated in ataxia-telangiectasia syndrome.
Quick Concepts:
Ataxia-telangiectasia labs
- Decreased IgA, IgG, and IgE
- Elevated AFP
- Lymphopenia
Summary:
Ataxia-telangiectasia is a neurocutaneous syndrome that is inherited in an autosomal recessive pattern. It presents with symptoms such as gait ataxia, spider angiomas, and immunodeficiency. Labs generally reveal elevated AFP and decreased IgA, IgG, and IgE.
Correct Answer:
Explanation:
The patient has symptoms of ataxia-telangiectasia syndrome. The difficulty maintaining his balance shows ataxia and telangiectasia appears in his eyes. Since IgA, IgG, and IgE levels are decreased, the child is also at risk for an increased frequency of infections. Immunoglobulin levels are depressed because this syndrome results from a deficiency of a tumor suppressor/serine-threonine kinase that links double-stranded breaks in DNA to cell-cycle arrest. Since lymphoid cells have rapid turnover, they will have a high rate of DNA processing errors and so will be more severely affected by a defect in DNA mismatch repair than other cell types with a lower rate of turnover. Alpha-fetoprotein levels are elevated in ataxia-telangiectasia syndrome.
Quick Concepts:
Ataxia-telangiectasia labs
- Decreased IgA, IgG, and IgE
- Elevated AFP
- Lymphopenia
Summary:
Ataxia-telangiectasia is a neurocutaneous syndrome that is inherited in an autosomal recessive pattern. It presents with symptoms such as gait ataxia, spider angiomas, and immunodeficiency. Labs generally reveal elevated AFP and decreased IgA, IgG, and IgE.