ghon focus vs caseating necrosis vs granuloma

[lazylarry]

i'm having trouble clarifying these. which one causes reactivation tb? tks in advance

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[LRAccord624]

i'm having trouble clarifying these. which one causes reactivation tb? tks in advance

Primary TB- ghon focus (fibrotic scar) in LOWER lobe. Ghon focus + hilar node involvment=ghon complex.

Reactivation= caseating granuloma (=granuloma with cheesy, necrotic material in the middle) in the UPPER lobe

 

[lemonade90]

Anytime you have a granuloma with mycobacterium, you should get caseation from the release of lipids from dead mycobacterium. Ghon complex is the primary infection (granuloma) in the lower/middle lobes+hilar lymph nodes. Fibrocaseation happens in reactivation or sensitized individuals in upper lobes. Not sure why the caseation is more prominent in the latter case, perhaps the body is sensitized so knows how to better attack?

 

[Leon22]

is it correct to describe primary tb coagulative necrosis and 2nd tb as caseous necrosis based on gross finding?
type of necrosis determined the type of tb?

 

[lemonade90]

is it correct to describe primary tb coagulative necrosis and 2nd tb as caseous necrosis based on gross finding?
type of necrosis determined the type of tb?

Caseation necrosis is a subtype of coagulative necrosis. But yes the gross findings should be different. Secondary Tb involves a bigger area and has lots of gross caseation visible.

 

[Phloston]

Anytime you have a granuloma with mycobacterium, you should get caseation from the release of lipids from dead mycobacterium. Ghon complex is the primary infection (granuloma) in the lower/middle lobes+hilar lymph nodes. Fibrocaseation happens in reactivation or sensitized individuals in upper lobes. Not sure why the caseation is more prominent in the latter case, perhaps the body is sensitized so knows how to better attack?

Well in the latter case the Th1 response is diminished relative to the primary response. The only reason you'd get a secondary response would be due to reduced immunity. Therefore, I'd assume an increased number of macrophages are needed/recruited for the secondary infection, leading to more substantial necrosis.

is it correct to describe primary tb coagulative necrosis and 2nd tb as caseous necrosis based on gross finding?
type of necrosis determined the type of tb?

No. For board purposes, TB is always caseous necrosis (same with fungi and Nocardia).

 

[lemonade90]

Well in the latter case the Th1 response is diminished relative to the primary response. The only reason you'd get a secondary response would be due to reduced immunity. Therefore, I'd assume an increased number of macrophages are needed/recruited for the secondary infection, leading to more substantial necrosis.

Yes, I understood that part. But for some reason I think you will get fibcrocaseous necrosis even if you completely cleared out the old Tb and then get reinfected again with more Tb. I don't know whether this is accurate but the pic in FA makes it seem this way and I can't remember what I learned in class. lol