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An 8 month old boy is brought to physician because of repeated episodes of pneumococcal pneumonia. Lab studies of serum show very low levels of IgM, IgG and IgA. Flow cytometry of a peripheral blood smear shows a near absence of CD19 cells, although levels of CD4 and CD56 cells are within normal limits. A bone marrow biopsy shows abnormally high numbres of cells with cytoplasmic mu chains, but none bearing surface IgM molecules. 1. What is your diagnosis why do you think this? 2. What protein is most likely deficient in this patient?

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The General Principles section of the USMLE covers these topics:
Biochemistry
Genetics
Microbiology
Pathology
Pharmacology


1. An 8 month old boy is brought to physician because of repeated episodes of pneumococcal pneumonia. Lab studies of serum show very low levels of IgM, IgG and IgA. Flow cytometry of a peripheral blood smear shows a near absence of CD19 cells, although levels of CD4 and CD56 cells are within normal limits. A bone marrow biopsy shows abnormally high numbres of cells with cytoplasmic mu chains, but none bearing surface IgM molecules. 1. What is your diagnosis why do you think this? 2. What protein is most likely deficient in this patient?





 
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