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Tuberculosis

 
  By : , NJ, USA       10.4.2010         Phone:-          Fax:-          Mail Now
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Tuberculosis or TB is one of the oldest diseases known to affect humans, caused by Mycobacterium Tuberculosis. More than 3.8 million cases were reported worldwide to the WHO in 2001, but because of lower levels of reporting, it is estimated that there were more than 8.5 million new cases in 2001. Ninety-five percent in Asia, around 5 million, and 2 million are thought to be in Africa. There were 1.8 million deaths from tuberculosis, 98% were from developing countries.

TB usually affects the lungs, but in about 35% of cases, other organs are affected as well. It is treatable in almost all cases, but if left untreated can be fatal in 5 years.



Natural Course of Illness

Exposure
The disease is transmitted from infectious patients with pulmonary TB to others by droplets. The bacilli that causes the illness is called *acid-fast* because of its high attraction to mycolic acid. AFB, or acid-fast bacilli are present in the sputum and transmitted by coughing, and sneezing. The droplet may remain in the air for several hours and may gain access to the air passages of other people when inhaled. Patients who have AFB negative respiratory cultures and those with extra pulmonary tuberculosis are less infectious. About 20 new people may be infected by each AFB positive patient.†

Infection to Disease
Once infected, developing the disease may depend on the exposed personís immunity. The clinical disease that immediately follows the exposure is called Primary Tuberculosis. It is usually seen in children up to 4 years. It may be severe but not transmittable in children. In older patients, primary TB is usually mild. Majority of infected patients who develop TB do so in 1-2 years. Usually, lesions heal and remain dormant. Dormant lesions that develop later in life become secondary TB. The risk of developing the disease is higher in adolescents and young adults. And it also increased in the elderly because of decreased immunity.†

Risk factors that increase development of the disease include: HIV positive and decreased immunity. Untreated TB is often fatal. One- third die in one year, and half in five years.†

Symptoms- Clinical Presentation

Tuberculosis is classified as pulmonary and extra pulmonary.†

Pulmonary TB can be categorized as primary and secondary. Primary TB presents as lesions in the lung and enlargement of the lymph nodes. The lung lesion usually heals and leaves a scar in the lung. In patients with decreased immunity, primary TB may progress rapidly into clinical disease. The primary site of infection enlarges, leading to the formation of a cavity in the lung. Lymph nodes may be enlarged, and other presentations may be fluid in the pleura- or a pleural effusion, pus in the pleura- or empyema and bronchiectatsis. The bacilli can also get into the blood stream and form lesions in different parts of the body, including meningis, or the covering of the brain.†

Secondary TB usually occurs in adults because of the activation of the bacilli that are dormant in the primary nodules. This can lead to cavities, and the patient becomes very ill, but most respond well to treatment.†

Signs and Symptoms of secondary TB include:†
- cough
- fever
- weight loss
- night sweats
- anorexia
- weakness
- blood in the sputum
- chest pain which is increased while breathing
- shortness of breath may be caused by extensive disease

Extra pulmonary TB can be†
1) Lymph node TB- painless swelling of lymph nodes mostly in neck area. These lymph nodes can become enlarged and may have drainage from it.
2) Pleural TB can present as fluid collection in the pleural cavity. Patient may present with fever, chest pain and shortness of breath. Chest x-ray may show cavity. AFB may be present in the fluid. Needle biopsy of the pleura is definitive diagnosis.
3) Empyema-collection of pus in the pleural cavity. X-ray may show air fluid levels. Fluid may be positive for AFB. Treatment is drainage of the fluid and medications.†
4) TB of upper airways- Larynx, pharynx and epiglottis may be affected. May present with difficulty in swallowing, and ulcerations maybe e present in examination of the larynx, Biopsy is required for diagnosis.
5) Genito-urinary TB-occurrence is around 15%. This happens secondary to blood spread. Pain while urinating, blood in the urine and flank pain may be seen. Urine examination and culture lead to 90% diagnosis. IVP measure lesions in the kidney.
6) Skeletal TB occurs in 10% of cases because of blood spread. Usually bigger joints are affected, such as spine, hips, and knees. Spinal lesions can lead to collapse of the vertebrae. Abscesses may form along the sides of the vertebral body. The compression of the spine may lead to weakness or inability to use lower extremities. This is a medical emergency. Drainage of the abscess should be done immediately. Bone TB usually responds to medication but in some cases, surgery may be needed.†
7) TB Meningitis-occurs in 5% of cases, usually happens in young children and immunosuppressed (HIV positive) adults. May present as headache, mental change, confusion, weakness, altered mental status, neck stiffness. Diagnosis is by lumbar puncture. AFB staining and culture of the cerebral spinal fluid may be done as well. CT scan and MRI may show hydrocephalus. If unrecognized and untreated, mortality is 100%. There is good response to treatment.†
8) GI TB- may present as abdominal pain, diarrhea, blood in the stool, and mass in the abdomen. Fever, weight loss and night sweats may be present. Surgery is needed as treatment.†
9) TB pericarditis- Fatality is up to 40%. Diagnosis is by echocardiogram and pericardiocentesis- or removing of fluid from the space around the heart.†
10) Miliary TB- caused by blood spread of Tuberculosis bacilli. Usually in children, it presents as primary TB and in adults as reactivation of old TB. It causes small seed-like lesion in different parts of the body. Fever, night sweats, anorexia, weight loss, weakness, and respiratory symptoms may be present.†

Diagnosis
There should high index of suspicion depending on history of exposure.†
Chest x-ray may show cavity infiltration.
Skin test may be done. It is called Mantoux test or PPD, where a small amount of tuberculin is injected into the skin. The reading is done in 48-72 hours after placement. A raised nodule is positive. There also can be false positives in skin tests. 1) Those who have been vaccinated with BCG vaccine or 2) Those infected with other Mycobacterium infections.†
Cultures- both blood and sputum can be cultured. Microscopy or smear of the sputum may show AFB positive bacilli. Cultures usually take 4-8 weeks to grow.†
Nucleic Acid amplification may be done of the sputum and may be done in a few hours.†

Treatment for TB
First line of drugs- INH, rifampin, pyrazinamide, ethambutol Ė for approximately 4-6 months.

Side effects of drugs
Rifamphin- rash, liver toxicity, orange colored urine
INH- fever, chills, hepatitis, peripheral neuritis, seizures
Pyrazinamide- increased uric acid
Ethambutol-optic neuritis

Prevention
BCG vaccination is recommended in newborns in areas where TB is common.







TAGS: Tuberculosis,   TB,   Symptoms of TB,   Types of TB,   Treatment for TB,  




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