Justice
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A 19-year-old man is evaluated after his seventh episode of bacterial sinusitis in the last 10 years. He has also had two episodes of bacterial pneumonia during the same time period as well as probable bacterial pneumonia when he was 7 years old. Quantitative serum immunoglobulin determination shows that the IgA is below the limits of detection and that the lgG and 1gM are both in the high-normal range. The patient is treated with oral amoxicillin and has a prompt response.
Which of the following diagnostic studies should be ordered next to help define the reason for the patients multiple bacterial infections?
A. Measurement of total hemolytic complement (CH50)
B. Lymphocyte subset quantification
C. Repeat quantitative serum immunoglobulin determination
D. Serum IgA subset quantification
E. Serum lgG subset quantification
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| WaqasQureshi
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D
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| nyimalay
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E
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| dr.wad
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D.....
selective IgA immunodeficiency.
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| cool doctor
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E
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| Markus2009
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E Rule out concurrent IgG subclass deficiency
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| Justice
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The correct answer is E
Although this patient has IgA deficiency, this disorder alone is not generally associated with multiple bacterial infections. The presence of low levels of one or more of the four lgG subsets is the most likely explanation for his increased bacterial infections, and serum lgG subset quantification should therefore be obtained.
Measurement of total hemolytic complement (CH 50) is unlikely to be helpful, since the complement deficiencies associated with multiple pyogenic infections are quite rare (with the exception of neisserial infections). Lymphocyte disorders that cause abnormal lymphocyte subset quantification are also unlikely to be associated with enhanced susceptibility to bacterial infections. Repeat quantitative immunoglobulin determination is unnecessary because of the small likelihood of laboratory error, especially since the lgG and 1gM values are normal or high normal. Since IgA was not detectable, serum IgA subset quantification cannot be done. Also, even the documentation of low or absent values for only one of the two IgA subsets would not satisfactorily explain this patients increased number of infections.
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