Clinical Presentation of Pulmonary Tuberculosis
PKGhatak,MD
Pulmonary
Tuberculosis presents in multiple ways.
Pulmonary
tuberculosis is a very old disease. Evidence of tuberculosis was
detected in 4,000 old Egyptian mummies. Description of TB like
disease was recorded in 3,500 old Sanskrit literature, and still, older evidence was uncovered in Israel in a skeleton found in an old
grave. Currently, pulmonary tuberculosis is still very much
prevalent globally and is a curse for people of Southeast Asian and
Northern African countries. 10,000 new cases were detected worldwide
and 1.5 million people died of tuberculosis in 2018.
Pulmonary
tuberculosis has several modes of presentation. The clinical
presentations of clinical illness due to TB vary according to the
prevailing standard of sanitation and public health of countries.
Latent
Tuberculosis in Western countries.
Immigrants
coming to western countries require to have a negative chest x-ray
as a prerequisite for a visa. Tuberculosis (TB) tests are mandatory in
many countries for employment in schools, universities, hospitals,
healthcare, nursing homes and would be new nursing home residents and
workers in the retail business. Some of the applicants react
positive to Interferon gamma release blood test or the old fashioned
TB skin test.
This positive TB tested people are completely symptom free, have no
indication of prior TB infection, and are unable to recall coming in
contact with an infectious TB patient.
A
careful review of a recent chest x-ray or CT chest will identify a
small nodule in the upper part of the lungs, and also occasionally a
small regional calcified lymph node. Induced sputum smears and
cultures are done routinely and are negative.
The
Public Health Department (PHD) must be notified and state mandated
treatment protocol and follow up are taken up by the PHD.
Reactivation
of Latent TB.
Two
ways the reactivation of latent TB present - Local spread and Pleural
effusion.
Local
spread.
Many immigrants from countries where TB is prevalent may not be
subjected to TB surveillance upon arrival in the new country. They
remain symptoms fee for a very long time until the cellular immunity
is reduced by an infection like HIV, and immunosuppressed conditions
due to Diabetes mellitus, prolonged use of corticosteroids,
immunosuppressed drug therapy in organ transplants and cancer
chemotherapy. The dormant TB bacteria residing within the macrophage
cells wake up and become metabolically active and begin to multiply.
Eventually, TB bacteria break up the cellular barrier and invade adjoining
tissues.
As TB becomes an active disease the patient may experience profuse night
sweats, unproductive cough, evening chills and a low grade fever and
loss of weight.
The clinical examination followed by laboratory tests reveals a positive Interferon
gamma release assay (IGRA) and a single pulmonary nodule in the upper
zone of the lung in the CT chest. These abnormal shadows often show two distinct densities
- a denser central core and a lighter peripheral cellular
infiltrate zone
The
major concern at this stage is – it is cancer or granuloma. TB
bacteria is one of the few other microscopic organisms that produce
granuloma.
The
most direct way to distinguish between the two is to obtain tissue by
skinny needle biopsy with ultrasound/ fluoroscopic guidance.
But if
the granuloma is due to TB infection that might contaminate the path
of the needle and might help to spread TB to pleura and subcutaneous
tissues.
The
alternative is to wait 3 to 6 months and obtain a repeat CT scan and
then evaluate the activity of the lesion and then decide when to
biopsy.
This
decision must depend on the best judgment of the attending physician and
the patient. There are risks both ways.
Induced
sputum for cytology for cancer and fungal and TB are also performed
as a part of the initial evaluation. Depending on the culture media used for
TB culture, positive growth may or may be available in 4 to 6
weeks. Bronchoscopic brushing and washings are examined for cancer
and infective agents. The success rate of identification of cancer/
infection is better by examining the bronchoscopy materials, but the
success rate is not 100 %. The IGRS test of bronchial brushing and wash fluid
containing mononuclear cells has a much higher rate of positivity of
IGRS compared to peripheral blood lymphocytes.
Pleurisy
and Pleural Effusion.
Clinical
presentation.
The onset of chest pain, fever, and mild non-productive cough suddenly occurs in young apparently young healthy individuals. Pleural space TB
inflammation takes place in one of the two ways - hypersensitive reaction and direct infection.
Hypersensitive
reaction.
It is
the usual mode. The initial symptom is a sudden onset of chest pain
aggravated by breathing. The two layers of pleura, rubbing against
each other during inhalation and produce chest pain. A few days or
weeks later the pain suddenly diminishes once the pleural fluid begins
to accumulate. Then the patient feels heaviness in one side of the chest
and may develop a low grade persistent fever.
In the pleuritic state, audible friction rubs on auscultation is
diagnostic of pleurisy but not diagnostic of TB pleurisy only. The
right sided pleural effusion is usually seen and less than 10 % of cases of TB
pleural effusion may be bilateral. The pleural fluid is easily obtained by bedside thoracentesis, at the
same time pleural biopsy is performed by a special needle (Abram's
needle). A pleural biopsy is safe because the lung is separated
from the pleura by a layer of fluid and the chance of pneumothorax is
minimal.
The TB pleural fluid is light yellow in color, the protein contains over 3 gm/dL, cell count 100 to 1000 /ml and predominantly lymphocytic, glucose content is less than 40 mg/dL, ADL (adenosine deaminase) test on T-lymphocytes is typically over 45U/L but below 200U/L. The ADL is the most sensitive (93%) and specific test (94%) for TB pleural effusion. IGRA assays are specific, but sensitivity is 70% in the
peripheral blood and 97% in pleural fluid lymphocytes. TB culture
grown in liquid media is in the 50 % range. TB
bacteria in smears are rarely seen in hypersensitive TB
pleurisy/pleural effusion. In
hypersensitive pleural effusion, a pleural biopsy may or may not show
caseating granuloma. If granuloma is present then a few TB bacteria can
be identified in
pleural TB infection.
TB infection of Pleura.
A
subpleural TB nodule ruptures in the pleural space. The escaped TB
bacteria infects the pleura. Occasionally the TB bacteria are carried into
the pleural space by the lymphatics. The
contamination of the pleura in one way or another result in pleurisy and
pleural effusion. The
clinical presentation, however, is a bit different. Here, any age
group of people may be infected, except children. The patients are
ill if they have progressive primary pulmonary TB infection. In latent TB patients, most patients are symptoms free prior to
pleural effusion. A
short period of pleuritic chest pain followed by pleural effusion
occurs like the hypersensitive pleural effusion.
Chest
X-ray reveals, in addition to plural effusion, the site of latent TB
infection. The character of pleural fluid is no
different from the hypersensitive pleural effusion and additionally,
RBCs in variable numbers are present. The pleural biopsy reveals
caseating granulomas and TB bacteria are generally identified in the granuloma. The smear of the fluid may not show TB bacteria but cultures in liquid media
are always positive. If the TB bacteria are scanty, they can be identified
by Nucleic Acid Amplification Test (NAAT)
Primary
Pulmonary Tuberculosis.
Primary
pulmonary tuberculosis is a global health problem. People in every country
of the globe are contracting pulmonary tuberculosis every year.
Two
factors have made tuberculosis eradication a daunting task. 1. TB
bacterial survival resiliency. 2. Handicapped immune system to fight
TB infection. Human
TB bacteria that produce primary pulmonary tuberculosis are called Mycobacteria Tuberculosis, in short MTB.
MTB
survival resiliency.
MTB
are rod shaped, nonmotile, slow growing bacteria and need oxygen to
grow. It lives inside Macrophages and multiplies under favorable
conditions. MTB has a three-layered cell wall. The multilayered
cell wall blocks TB drugs to enter the bacterial body in sufficient concentration to kill the MTB.
Handicapped
Immunity.
In any
infection, both the Cellular and Humoral immune systems are
activated. But in MTB infection the Humoral immunity remains largely
inactive. The CD4 cells, macrophages and other immune T-cells collectively fight
against MTB invasion.
Mode
of MTB primary pulmonary infection.
MTB is
a respiratory pathogen, human to human transmission occurs via
infected droplets. Causal contact with an open MTB case (TB
bacteria in sputum) does not cause infection; prolonged
contact and repeated exposures over months are necessary. Overcrowded
prisons, sailors in submarines, residents in dormitories, hostels and nursing homes are
ideal places for MTB transmission.
A
majority of inhaled droplets are caught by the mucociliary escalator
and are eliminated. A few MTB reaches the alveoli. MTB penetrates the alveolar wall and enters the interstitial tissues and is promptly
caught and swallowed by the tissue macrophages. Macrophages are
unable to digest the MTB due to the presence of enzymes in bacteria that
neutralize the digestive enzymes of macrophages, and the bacterial wall is
indigestible. Additional macrophages and lymphocytes accumulate
around the infected macrophage and a nodule is formed. 85 % of the
initial infections are contained and confined locally. But MTB
remains dormant inside the infected macrophages. This infected nodule
becomes Latent TB.
Progressive
Pulmonary TB.
People
with suppressed cellular immunity are unable to limit the initial
infection. The MTB multiplies and break out of macrophages and infect the adjoining areas, some of the infected macrophages carry the
bacteria to the regional lymph follicles/nodes and these two infected areas
are collectively called the primary complex. Further
growth and progression of infection continue. 6 to 9 months after
the initial infection the patient starts to experience symptoms.
In
advanced countries, only 1/3 of newly diagnosed cases are due to
fresh infections and the rest 2/3 are due to the reactivation of latent
TB.
Symptoms are - lack of energy, easy fatigue, anorexia, loss of weight, short but
successive unproductive coughs and profuse night sweats are common.
Further
progression of the disease produces: 1. Wide areas of Pulmonary
infection and is known as primary progressive Tuberculosis. 2. Hemoptysis.
3. Miliary TB.
Primary
Progressive Pulmonary Tuberculosis.
These
patients are sick and weak. Persistent low grade fever, wasting of
muscles, anemia, cough productive mucopurulent sputum and occasional
streaks of blood in sputum is present. Confirmation of pneumonia
is not difficult but there are no special clinical features of MTB
pneumonia.
Chest
x-ray shows infiltration in the upper zone of the lung, usually on the
right side and spread of the disease in the adjoining lobes. In some
cases, thick walled cavity is seen in the upper lobe or apical portion of the middle lobe. In nursing home patients, middle lobe and lower lobe
infiltrations are common.
Sputum
smears and cultures are the cornerstones of MTB diagnosis. IGRA assay
of peripheral blood is both sensitive and specific. In occasional
cases, NAAT (Nucleic acid amplification) test may be necessary.
Hemoptysis. Blood-streaked sputum is an indication of the progression of disease and
destruction of the lungs. That leads to bringing up frank red blood.
Almost
all patients present with hemoptysis undergo bronchoscopic examination.
It not only helps to diagnose MTB but also eliminates the possibility of lung cancer and fungal infection.
Miliary
Tuberculosis.
MTB not only destroys the lung parenchymal tissues but also
penetrates blood vessels and spreads far and wide. MTB can also spread
via lymphatics. The tissues rich in oxygen support further MTB
growth. Lungs, meninges, bone marrow, and kidneys are common sites of
extrapulmonary TB infection.
The
patients are very malnourished, very weak and unable to cough
properly. Sputum production is generally absent or minimal. Patients
are febrile and may show abnormal liver, renal functions and
electrolyte imbalance. Both acute and chronic phase reactants are
positive. In severely immunosuppressed patients with low CD4 cell
count, the TB skin tests and IGRS test may be negative.
The chest x-ray is virtually diagnostic, and a bone marrow biopsy showing
granulomas and MTB are easily demonstrated. Bone marrow cultures are
necessary for the final diagnosis and also for the detection of drug resistance. Concurrent HIV infection must be eliminated by proper tests.
All Pulmonary MTB cases must be reported to the local Public
Health Department (PHD). PHD use approved treatment protocol, makes sure of TB
drug delivery and compliance of patient in taking TB drugs, and performs
contact tracing and chemoprophylaxis of appropriate people.
In
addition to these modes of presentation of MTB pulmonary infections, some unusual presentations are
also identified in unsuspected patients on bronchoscopy. The use of more advanced tests helps to identify MTB infections. That part is not discussed here.
Non-MTB mycobacterial pulmonary infections are less common but the number of new cases is growing. This subject is discussed in a separate place.
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