Tuberculosis: Two forms
of the disease
-
Primary infection (Ghon Complex)
-
Secondary (reactivation tuberculosis)
a
little more info on each…
Primary Pulmonary
Infection
-
Children most commonly affected
- GHON
complex: Local lymphatic dissemination of bacteria with
hilar adenopathy
1) Parenchymal
subpleural focus
à
where you inhale the organism and are left with a
granuloma in your subpleural area (as we saw
previously); causes initial infxn and damage
2) Enlarged caseous
lymph nodes draining (hilar lymph nodes) the parenchymal
focus (in other words, live organisms will be drained
through the lymphatics to the hilar lymph nodes causing
the same type of pattern there
à
peripheral nodule with a central nodule; these nodules
usually become fibrotic and calcify over a period of
time)
- Few
clinical manifestations
- usually asymptomatic
- Fever, fatigue
- Will
rarely Progress from primary tuberculosis to
disseminating tuberculosis
The
patient has inhaled a tuberculosis organism and it has
caused permanent destruction of the lung subpleurally.
Over time this will calcify and you will be able to see
it on an x-ray. We don’t normally remove calcified
nodules in the lung because they are usually benign and
usually just old tuberculosis.
To the right is a GHON complex.
Notice that you have the same histological appearance (granuloma,
giant cells) in both the subpleural lesion and the hilar
region. Usually, if you are healthy, you can wall off
the nodules and have calcification.
Reactivation/Secondary
Pulmonary Tuberculosis
-
Adults are affected
- Have had tuberculosis as a
child; have a GHON complex that has been walled off and
is fibrotic/ calcified.
- Upper
lobe disease (necrotizing granulomas) predominates
- Upper lobes involved almost exclusively
because oxygen tension is greatest in the apices.
-
Cavitation of upper lobe
-
Extra-thoracic sites of disease spread by hematologic
dissemination
The
lung of someone who has had reactivation tuberculosis.
All of the necrosis is in the apex, really close to the
pleural space. These areas will become fibrotic in an
attempt to wall off the entire area.
Miliary/disseminated tuberculosis–
when the organism spreads hematologically through the
lungs and other parts of the body. Yellow areas (the
little yellow dots inside the circle) are areas of
necrosis. This basically causes bronchopneumonia with
no resolution once its miliary.
(Called
miliary tuberculosis after the milate seed – a yellow
bird seed.)
Another
picture of miliary tuberculosis. Once again, once
the patient has milary TB, the organism can spread
hematologically throughout the body (but, in most cases,
the patients are able to wall off the infection
completely and this doesn’t happen).
A chest X-ray of someone with miliary
tuberculosis. The diffuse
white stuff is the tuberculosis particles on both sides
of the lung.
Causative Organisms
- Mycobacterium species is
usually the likely organism but there are other
organisms that are acid-fast bacilli and may not be
tuberculosis:
- Actinomyces
- Nocardia
- There
are also many species associated with human infection
- M. tuberculosis
- M. bovis
- M. leprae
- M. africanum
- Atypical Mycobacterium
- M.avium (Seen in the HIV/immunocompromised
host)
Summary
(This is where it finally comes together and makes
sense): In reactivation disease patients will get apical
disease. They will usually be able to wall it off and
it will become fibrotic or caviteric. In some patients,
however, there will be the development of further
problems with miliary tuberculosis.
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