Tuberculosis is a disease caused by Mycobacterium tuberculosis, a bacteria that primarily infects the lungs.  With widespread screening of high-risk children, the incidence of tuberculosis in North American children is low.  Worldwide, tuberculosis remains a serious public health threat, with almost 1.3 million new cases and 450,000 deaths in children each year.  It is estimated that nearly one-third of the world's population are Mycobacterium tuberculosis carriers.  Most children infected with the bacteria have no symptoms, however children are more likely than adults to develop tuberculosis disease from a carrier state.  Infected infants have a 40% chance of developing tuberculosis and this rate increases to the adult rate (5-10%) as the child ages.  Mycobacteria grow slowly and tuberculosis disease may not become apparent for years (sometimes decades) after infection.  Treatment is accomplished with multiple antibiotics given over a long period of time (6-9 months).  A vaccine is available, however it is not routinely used in the United States, since it is only partially effective and make the common tuberculosis skin test (PPD) inaccurate.

What causes tuberculosis?

Mycobacterium tuberculosis, a bacteria that is carried by about a third of the world's population.  It mostly affects the lungs and lymph nodes (and less commonly bones, brain, and kidneys).  Mycobacterium tuberculosis is primarily found in non-industrialized nations with poor living conditions, inadequate disease screening and treatment, and high rates of HIV-infected individuals (who are at high risk for developing and spreading tuberculosis). 

How is tuberculosis transmitted?

Transmission occurs by way of respiratory droplets (i.e., from a cough or sneeze), mostly from infected adults.  Children have less bacteria present in coughed up material (i.e., sputum) and have a less forceful cough.  Therefore children rarely spread the disease. 

Tuberculosis is rarely passed from pregnant mothers to the fetus.

What are the symptoms of tuberculosis?

Most children have NO symptoms!

Severe or persistent infection may cause:

• Cough
• Fever
• Night sweats
• Poor weight gain
• Swollen lymph nodes
• Ill-feeling
• Flu-like symptoms

25–30% of children with tuberculosis will develop disease outside the lungs.

How is tuberculosis diagnosed?

A tuberculosis skin test with purified protein derivative (PPD) is the primary screening test.  A small amount of Mycobacterium tuberculosis protein is injected, with a very small needle, just under the skin.  After 48 to 72 hours, the site is inspected for swelling and redness.  If the swelling is larger than 0.5 to 1.5 cm (depending on the child's risk factors), the test is considered positive and the child should be treated.  Special tests may be done to confirm the diagnosis and determine the bacteria's sensitivity to antibiotics.

A chest X-ray should be performed to determine if lung lesions are present.

How is tuberculosis treated?

A regimen of multiple antibiotics is typically given for 6-9 months.  The choice of antibiotics depends on the sensitivity of the bacteria isolated from the child.  A typical treatment regimen includes isoniazid (INH) and rifampin for 6 months, with pyranzinamide given for the first 2 months.  It is important for infected children to complete the full course of antibiotics (even if there are no symptoms) to prevent developing a carrier state or antibiotic-resistant bacteria.

What are the possible complication of tuberculosis?

Lungs - A pneumonia-like lesion may develop.  Inflammation at the site of infection may cause fluid to collect outside of the lungs (i.e., a pleural effusion) that may press on the lung, restricting breathing.  Inflammation may cause pain (i.e., pleurisy) as the lung surface rubs against the membrane surrounding the lung, called the pleura.  A lung cavity may develop that can hold fluid, leading to other types of bacterial infection.

Lymph nodes - The most common form of tuberculosis outside the lungs in children is lymph node disease.  Typically the lymph nodes in a area that drains the lymph from a tuberculosis lesion are affected.  The lymph nodes in the anterior neck are often involved, since they drain lymph from the lungs where tuberculosis lesions are common.  Often a single lymph node grows slowly to form a large, rubbery, non-tender mass under the skin.  This mass may decay from the inside-out, and may drain to the outside.  Often, surgery is needed to remove the infected lymph node to confirm the diagnosis.  Antibiotics are still required after lymph node removal.

Heart (pericarditis) -  In 0.5–4% of tuberculosis cases in children, the membrane surrounding the heart may become inflammed.  Fluid collects outside the heart in the pericardial space.  Increasing pressure may cause heart failure.

Central nevous system (meningitis) - Meningitis is a rare (0.3% of cases in children) but feared complication of untreated tuberculosis.  Spread of the bacteria to the cerebral spinal fluid can cause a lesion to develop in the brain.  This can lead to seizures, blockage of spinal fluid (hydrocephalus), stroke, swelling of the brain, or death.

Skin - After the bacteria enters a break in the skin, a small reddish-brown bump slowly widens and ulcerates.  The result is a shallow, painless, ulcer that heals slowly over months.  Only 1-2% of children with tuberculosis develop this type of skin lesion.

Bones and joints - Bone and joint infection complicating tuberculosis is rare in children.  The vertebrae of the spine are the most commonly affected (called Pott disease), and the resulting spine damage can lead to a permanent abnormal curve of the spine.

Gastrointestinal - Tuberculosis occassionally affects the gastrointestinal tract.  Shallow ulcers and lymph tissue enlargement may develop.  This may be confused with inflammatory bowel disease, especially when it occurs in the last part of the small intestines.

Genitourinary - Genital or kidney infection can occur in both male and female children.  This complication of tuberculosis is more common in chronically infected adults than in children.

Perinatal infection - Infected mothers can spread tuberculosis to a newborn infant.  Symptoms are similar to many other causes of sepsis in newborns.  Diagnosis can be difficult and many children will die unless treated with appropriate antibiotics quickly.

Coinfection with HIV - Children with HIV have 30 times the risk for developing tuberculosis.  The bacteria are more likely to be antibiotic resistant, and death is common.

Disseminated disease - Tuberculosis can affect nearly any organ system of the body.  The bacteria grows slowly and systemic disease may require years without treatment.  Tuberculosis can show many different symptoms or no symptoms at all.  A tuberculosis skin test (PPD) should be done for all children with a confusing systemic disease or for those planning on starting immunosuppressive medications.

DrTummy's experience...

Tuberculosis (in kids) is rare in the United States.  I haven't seen any cases of active tuberculosis (in kids) in my first 7 years of practice.  Pediatricians check for this disease frequently because it is easy to miss and could be made worse by some of the medications we use.  It is more important to consider this diagnosis when there are obvious risk factors (i.e., foreign travel, exposure to an adult with a chronic cough, incarceration, etc.).

Photo 1 - Tuberculosis Chest X-ray with TB cavity right upper lobe. Figure 1. Arrow points to a cavity in patient's right upper lobe. from Core Curriculum on Tuberculosis - What the Clinician Should Know. 4th ed. 2000. Division of Tuberculosis Elimination, US Centers for Disease Control and Prevention (CDC).  Used with permission.

Photo 2 - ID#: 8438 Description: Under a high magnification of 15549x, this scanning electron micrograph (SEM) depicted some of the ultrastructural details seen in the cell wall configuration of a number of Gram-positive Mycobacterium tuberculosis bacteria. CDC. Used with permission.