Tuberculosis
(TB) Introduction: Tuberculosis is a potentially
debilitating respiratory disease, which if not treated can become systemic and
is a serious threat to a person's life. 50% of infected people will die within
5 years, if tuberculosis is untreated (Ref.1, p.521) and most of them will die
within 18 months. The good news is that TB can be treated successfully with a
combination of drugs, but it takes long, is cumbersome and needs close supervision
by an infection specialist. The bad news is that new resistant strains
of TB have developed in the past few years in people with a paralyzed immune system
such as AIDS, or people with cancer and leukemia. Natural progression
of the disease:There are three strains of tuberculosis, Mycobacterium
tuberculosis, Mycobacterium bovis and Mycobacterium africanum. In industrialized
countries transmission from person to person usually occurs via micro droplets
in the air from a person that has tuberculosis of the lungs or the larynx and
who coughs the bacteria into the environment. In this way Mycobacterium tuberculosis
can stay in the air for several hours and thus increase the probability of spread
from person to person (Ref. 10, p.1193).
| The three stages of
tuberculosis (TB): | | 1.
Primary infection within the lung tissue: this is the usual way how tuberculosis
starts. 2. Latent or dormant stage of tuberculosis:
often tuberculosis goes "underground", on the surface not progressing
for up to 1 or 2 years, but the TB bacterium is live wherever it incubates and
there are silent tissue reactions. 3. Active tuberculosis
in various organ systems: As shown in the next table, tuberculosis tends
to express itself in 11 different organ systems masquerading as distinct clinical
entities despite the same underlying TB pathogen. |
When the bacterium is inhaled, it forms the primary infection
within the lung tissue, which may go undetected, if no cough or other
symptoms develop. On other occasions TB might be diagnosed at this stage and treated
very effectively. It may then lay dormant (latent of dormant
stage of TB) and take several months or 1 to 2 years before it gets
reactivated. All along the TB bacterium is alive, but surrounded by granulation
tissue (one of the histological markers, with live tuberculosis bacteria in the
center). The third stage is active tuberculosisin
various organ systems (pulmonary TB, meningeal TB, miliary TB, tuberculous peritonitis,
lymph gland TB, tuberculous pericarditis, TB of bones and joints, liver TB, gastrointestinal
TB, TB of wounds and skin, Genitourinary TB). Tuberculosis symptoms: In
primary infection with TB (the first stage of TB) the patient just does not feel
well. There likely is a cough for a few weeks, but a smoker might think that it
is just a smoker's cough, whereas a non smoker may blame it on a "regular
cold or virus". In primary TB infection there is formation of granular tissue
around the TB bacteria as a result of an inflammatory reaction. This is
called a "caseous nidus" and this can rupture open and get coughed up.
The result is that the patient may see some cottage cheese like material mixed
into the phlegm that was coughed up. At this point in time there would be subtle
X-ray changes
on a chest X-ray. In adults there would be nodular scars on the upper lung fields,
called "Simon foci", from which the TB continues in the later stages.
In children the initial nodular changes are in the middle and lower lobes of the
lungs, which in that age group are better perfused. Children also get a prominent
hilar lymph gland reaction as well as more commonly pleural effusions, which shows
up on X-rays. After the dormant stage there is a sudden occurrence where TB either
flares up in the lungs or as tuberculous meningitis as a neurological disease.
TB is a great masquerator as it can also present as various system diseases, as
already mentioned above. and depicted in the table below.
| Third stage tuberculosis
and treatment | | Name
of Tuberculosis: | Comments: |
| primary
pulmonary tuberculosis | lungs are most
commonly affected | | meningeal
tuberculosis | this serious life threatening
neurological complication needs prompt treatment |
| miliary tuberculosis |
generalized tuberculosis, which originated from the lungs via the blood stream
or via the lymphatic system | | tuberculous
peritonitis | originated from abdominal
TB lymph glands or TB infested ovaries or tubes |
| lymph gland tuberculosis | starts
from the hilar lymph nodes and can spread to the upper mediastinum |
| tuberculous
pericarditis | TB may spread from mediastinal
lymph nodes or from tuberculous pleuritis into the sac around the heart (pericarditis) |
| TB
of bones and joints | common in children
where bones are still growing; Pott's disease affects two adjacent vertebral bodies,
can cause paraplegia, when vertebral bone collapses |
| liver TB | with
advanced TB of lungs and miliary TB liver involvement is common |
| gastrointestinal
TB | only in chronic TB such as in cavitary
TB of lungs; more common in bovine TB |
| TB of wounds
and skin | due to Mycobacterium avium
(bird transmitted TB variety), found in patients with AIDS, organ transplants
or in patients with hairy cell leukemia |
| genitourinary TB | Kidneys
are affected frequently with TB. Common in young women who recently got TB due
to vascularity of fallopian tubes | Tuberculosis
treatment Signs and symptoms as well as treatment are very
much determined by the anatomical location of TB. I will comment in the following
what treatments are used for the various forms of tuberculosis.
Primary
pulmonary TB or early stage 3 pulmonary disease When the
tests are positive for TB, this condition is treated for 3 months with a combination
of rifampin, clarithromycin and ethambutol. More serious invasive cases are treated
with 4 to 6 drug combinations simultateously. In the past partial lung resections
were often done, which is now reserved for the resistant cases in a young patient
who is otherwise healthy.
Tuberculous
pericarditis This more rare presentation
of TB originates usually through spread from the perihilar lymph glands that penetrate
the pericardial sac or from a tuberculous pleuritis (effusion within the chest
cavity from TB of the lungs). Clinically there are signs of cardiac failure with
neck vein distension and shortness of breath. X-rays show an enlarged heart and
pericardial fluid. A positive tuberculin skin test in combination with the above
clinical signs makes the diagnosis very likely and warrants antituberculous multi-drug
therapy. A good response to this treatment confirms the specific diagnosis of
tuberculous pericarditis and prevents potentially life threatening diagnostic
procedures such as surgical drainage of the cardiac effusion and diagnostic biopsy
of the pericardium.
Liver
TB The liver is often secondarily infected with patients with
advanced lung TB or in patients with miliary TB. The symptoms likely will be due
to the underlying other forms of tuberculosis. However, in the workup the patient
is being noticed to be jaundiced and the liver enzymes are elevated indicating
that the TB has spread into the liver. As invariably live TB is easily curable
when the primary TB is being treated, the diagnosis of liver TB is only important
to note in the sense that two commonly used antituberculous drugs, namely isoniazid
and rifampin, are hepatotoxic and should be avoided initially in these situations.
Instead the clinician will use a combination, which includes only isoniazid (not
rifampin), so that this can be stopped, if there is a worsening of the liver condition.
Newer antituberculous drugs can be utilized that are not as hard on the liver,
but are more expensive.
Gastrointestinal
TB As the gastrointestinal tract is relatively immune from
TB bacteria, it takes enormous amounts of the bacteria such as in cavitary lung
TB to infect the gut. In this case the patient coughs up TB bacteria and then
swallows them, eventually invading the lining of the gastrointestinal tract. In
development countries where milk is not pasteurized, bovine TB is commonly infecting
the gastrointestinal tract. Ulcers of the mouth and pharynx as well as tuberculous
lesions in the small intestine are common. An inflammatory mass may present like
an intestinal cancer lesion, but when laparotomy is done, it is apparent that
this is tuberculous in nature. Therapy consists of resection of the affected bowel
area in combination with multi-drug antituberculous therapy.
TB
of wounds and skin TB disease of
the skin and of wounds is usually found in patients who have a weakened immune
system, because of AIDS where the cell mediated immune system is paralyzed through
the AIDS virus, or in patients with hairy cell leukemia where the leukemia has
destroyed the cell mediated immunity. Also, in patients who have received organ
transplantation and who are on maintenance immunosuppressive therapy skin infestation
with a number of TB related Mycobacteria strains are occasionally found. After
identification of the causing agent combination antituberculous drug therapy is
given for 3 to 6 months.
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