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  1. #1
    USMLEbloggerMike's Avatar
    USMLEbloggerMike is offline Newbie 510 points
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    The Tuberculous Granuloma is High Yield for the USMLE

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    The Tuberculous Granuloma is High Yield for the USMLE

    Ahh the Granuloma - a great example of topic that overlaps multiple subjects and any topic that brushes borders with the likes of pathology, immunology and microbiology make for great questions. Here are 5 steps to the granuloma in perfect 3rd grader doodle form:


    Step 1:
    Inhale the red, ACID FAST rod



    M. tuberculosis is only acid fast why?
    B/c of the MYCOLIC ACID in the cell wall resists decolorization with acid-alcohol and so it remains red which is the color of the initial stain, carbol fuchsin.
    What else stains acid fast? Nocardia which is “partially acid fast”







    Step 2: Phagocytosis by alveolar macrophages


    Circulating monocytes roll on the vascular endothelium (d/t selectins) and adhere to it (d/t ICAMs) and then transmigrate into the affected area where they are called tissue macrophages.

    Macrophages are the main players in the formation of a granuloma
    Step 3: Antigen Presentation


    Step 4: T Cell Activation

    CD4 T Cells are involved
    The TH1 subtype
    No CD4 T Cells? No Granuloma. AIDS patients who loose their CD4 t-cells well before loosing their CD8 T Cells will make very weak if any granulomas.

    Step 5: Macrophage Activation

    Did I mention what the main player of a granuloma is? Oh yea, its the macrophage.
    The Caseous Granuloma


    Note that the caseous necrosis is cottage cheese like and is due to the destruction of the M. TB organism's cell wall's mycolic acids (mycolic acids are lipids).

  2. #2
    IMG SURVIVOR's Avatar
    IMG SURVIVOR is offline Moderator 536 points
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    dude standing ovasion to you, thats the best freaking explanation about that I have ever heard inmy life, and the pictures are so suitgeneris that make it unforgetable.

    You need to keep doing it with your own drawings, are better and more fun.

    at the end you might want to add some real slides, just so people see the real thing.
    Moderator: USMLE AND Residency Forums.

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    why even bother with the obvious. Just know where you are need it and where you can help the most.

  3. #3
    IMG SURVIVOR's Avatar
    IMG SURVIVOR is offline Moderator 536 points
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    a found this
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    Moderator: USMLE AND Residency Forums.

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    why even bother with the obvious. Just know where you are need it and where you can help the most.

  4. #4
    IMG SURVIVOR's Avatar
    IMG SURVIVOR is offline Moderator 536 points
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    And Xray I hope you guys can see the problem in the upper lobe
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    why even bother with the obvious. Just know where you are need it and where you can help the most.

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    IMG SURVIVOR's Avatar
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    On closer inspection, the granulomas have areas of caseous necrosis. This is very extensive granulomatous disease. This pattern of multiple caseating granulomas primarily in the upper lobes is most characteristic of secondary (reactivation) tuberculosis. However, fungal granulomas (histoplasmosis, cryptococcosis, coccidioidomycosis) can mimic this pattern as well.



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    why even bother with the obvious. Just know where you are need it and where you can help the most.

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