Tuberculosis

What is Tuberculosis?

Tuberculosis (TB) is an infection that occurs due to inhalation of the bacteria Mycobacterium tuberculosis.  Patients may initially have mild chest pain and respiratory symptoms weeks after infection.  They then enter a dormant (latent) stage in which the bacteria reside in the lymph nodes and are usually asymptomatic.  Months to years later, factors such as immunodeficiency (HIV-AIDS) can cause reactivation of tuberculosis infection, leading to weight loss, anorexia, night sweats, fever, productive cough, and hemoptysis.  Patients with some forms of tuberculosis have what is called miliary disease.  That means that the bacteria has disseminated to all of the major organs and tissues like “millet seeds.”

Risk factors may include travel to a region where the disease is endemic or exposure to an infected person.  Due to the importance of this condition, it is critical that patients understand its causes, symptoms, and treatment.

What Causes Tuberculosis?

Tuberculosis is caused by inhalation of Mycobacterium tuberculosis into the lungs.  Some individuals clear the infection immediately.  However, a certain percentage of patients develop primary disease in which the bacteria enter the lungs and infect regional lymph nodes in the chest.  Latent infection usually follows, where individuals are typically asymptomatic.  A subset of patients may develop reactivation tuberculosis after years of latent infection.  This is characterized by a cough and systemic symptoms.

Risk factors of infection include:

• History of incarceration
• Homelessness
• Prior history of tuberculosis
• Travel to an area where TB is endemic
• Exposure to an infected person

How Common is Tuberculosis?

This condition is common in the United States, but its prevalence worldwide is even more staggering.  Greater than 2 billion people have latent tuberculosis worldwide – this makes up about 1/3^rd of the population.  About 10 million people acquired tuberculosis and nearly 2 million people died of tuberculosis in 2015.

Uncomplicated cases may be managed by primary care physicians, but atypical or severe cases usually require referral to a pulmonary medicine or infectious disease specialist.

Signs and Symptoms

Many cases of primary tuberculosis are asymptomatic.  If patients develop symptoms, they typically include fever and chest pain.  This may occur due to enlarged lymph nodes in the chest.

Reactivation tuberculosis typically causes the slow onset (>2-3 weeks) of the following symptoms:

• Cough
• Hemoptysis – coughing up blood
• Chest pain
• Shortness of breath
• Weight loss
• Fatigue
• Fever (temperature > 101 F)
• Night sweats
• Lymphadenopathy – enlarged swollen lymph nodes

These classic symptoms may not be seen in the elderly.

Diagnosis

The diagnosis of tuberculosis is suggested based on symptoms and physical examination, but typically confirmed with laboratory and imaging studies.  Patients that are a public health risk for spreading the infection are usually placed on respiratory isolation (airborne precautions) and admitted to the hospital.

Your doctor will usually order a chest x-ray to evaluate for characteristic findings of reactivation tuberculosis such as cavitary lesions in the upper lungs.  If these findings are consistent, they will then order sputum samples.  Your doctor usually obtains 3 samples of your sputum 8 hours apart.  Sputum tests usually include acid-fast bacilli (AFB) smear, mycobacterial culture, and nucleic acid amplification testing.

Furthermore, you doctor will typically order a tuberculin skin test (PPD) or interferon-gamma assay.  During the tuberculin skin test, a healthcare provider will inject a small amount of test reagent under the skin on a forearm.  Swelling in the area (usually >5-10 mm) 2-3 days after injection is considered a positive test.  This only tells you that you have been previously exposed to tuberculosis, not necessarily that you have an active infection.

Tuberculosis Medication

Treatment of latent tuberculosis typically involves 9 months Niazid (isoniazid) or 3 months of weekly Niazid (isoniazid) and Priftin (rifapentine).

The treatment of active pulmonary tuberculosis generally involves an intensive phase followed by a continuation phase.  During the intensive phase, you will usually receive the following 4 medications for 2 months:

• ‎Niazid (Isoniazid)
• Rifadin (Rifampin)
• Pyrazinamide
• Myambutol (Ethambutol)

During the continuation phase, you usually receive 2 drugs for at least 4 months:

• ‎Niazid (Isoniazid)
• Rifadin (Rifampin)

Your doctor will likely obtain repeat sputum samples for AFB smear and culture while you are on therapy.  These usually occur at monthly intervals until 2 months of consecutive cultures are negative for infection.