new_n_lost
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A 4-year old boy with recurrent infections caused by Streptococcus pyogenes, Hemophilus influenza, and Pneumocystis carinii was admitted to the hospital following a 3-day sinus infection. His mother noted that he had developed a productive cough, now had a high fever. His white blood cell count was 4200/ul (normal count 5000-9000/ul). Twenty-six percent of his white cells were neutrophils (very low), 56% were lymphocytes (normal), and 28% were monocytes (elevated). A serum work-up revealed that his IgG level was 25 mg/dl (normal 600-1500 mg/dl), IgA was undetectable (normal 150-225 mg/dl) and his IgM level was 210 mg/dl (normal 75-150 mg/dl). A flow cytometric analysis of his peripheral blood cells revealed that all of his B cells were IgM+, IgD+. The boy may be suffering from:
A) Leukocyte Adhesion Deficiency
B) Systemic Lupus Erythematosus
C) Hereditary Angioneurotic Edema
D) X-Linked Agammaglobulinemia
E) Severe Combined Immunodeficiency
F) X-Linked Hyper IgM Syndrome
G) Paroxysmal Nocturnal Hemoglobinuria
H) DiGeorge Syndrome
I) Wiskott-Aldrich Syndrome
J) Selective IgA Deficiency
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| doc179
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F?
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| indidoc1
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I can't remember if neutropenia is associated or not but other features resemble Hyper IgM
So.. F
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| keepgoing
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F
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| new_n_lost
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F The activated T cell expresses surface CD40L. CD40L then interacts with CD40, which is constitutively expressed on the B cell, and this cognate interaction induces B cell proliferation, differentiation, and heavy chain isotype switching to IgG, IgA and IgE. T cell derived cytokines also participate in this class switching. In hyper IgM syndrome, CD40L is mutated preventing its interaction with CD40 on B cells. This prevents isotype switching. Consequently, IgM antibodies accumulate, whereas little IgG, IgE or IgA antibodies are produced. Patients with X-linked hyper IgM syndrome are highly susceptible to infection with pyogenic (pus-forming) bacteria such as Streptococcus pyogenes and Haemophilus influenzae because they are unable to produce an opsonizing IgG antibody responses to these pathogens. The polysaccharide capsules of these bacteria are resistant to destruction by phagocytes unless they are opsonized. IgG is an opsonizing immunoglobulin beacuse it binds to IgG-specific Fc receptors expressed by phagocytes. Patients with hyper IgM syndrome also have defective cell mediated immunity because of an inability of their macrophages to be optimally activated. Such activation also depends upon engagement of CD40 on macrophages with CD40L on T cells.
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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