Definition

Tuberculosis is an infectious disease that primarily targets the lungs. In miliary tuberculosis, however, the infection caused by Mycobacterium tuberculosis spreads widely through the bloodstream, impacting multiple organs throughout the body. Before antibiotics were available, miliary tuberculosis mainly affected infants and young children. Currently, it is more prevalent among adolescents, young adults, and the elderly, with men being affected slightly more than women.

Causes

Miliary tuberculosis is caused by the bacteria called Mycobacterium tuberculosis, known for its acid-resistant cell wall, which makes it detectable through an acid-fast bacillus (AFB) test. Humans are the main hosts for this bacterium, and transmission occurs through airborne droplets released by coughing or sneezing. These bacteria can remain suspended in the air for several hours.

When M. tuberculosis enters the body, a healthy immune system can often keep it in check, resulting in latent tuberculosis—a non-contagious, symptom-free state. However, if immunity weakens, latent tuberculosis can progress to active tuberculosis, which is both symptomatic and infectious.

Risk Factor

Miliary tuberculosis was more frequently observed in infants and children until the 1980s, but it now also affects adults due to immune system declines linked to various factors. These include:

• HIV/AIDS
• Heavy alcohol use
• Malnutrition
• Chronic kidney disease
• Diabetes
• Cancers of the lung, neck, or head
• Pregnancy or recent childbirth
• Prolonged dialysis

Medications that suppress the immune system also increase susceptibility to miliary tuberculosis. Such drugs are often prescribed to patients undergoing organ transplants, cancer treatment, or treatment for autoimmune conditions, where the immune system mistakenly attacks the body's own tissues.

Symptoms

Symptoms of miliary tuberculosis may progress gradually over months and include fatigue, weight loss, and headaches. Additionally, signs of systemic infection commonly associated with miliary tuberculosis are:

• Mild fever
• Persistent cough
• Swollen lymph nodes across the body
• Enlarged liver or spleen
• Pancreatic inflammation (pancreatitis)
• Impaired function of various organs, including the adrenal glands

Diagnosis

Diagnosing miliary tuberculosis can be challenging due to the difficulty of detecting bacteria in organ samples. Typically, the doctor will review symptoms and medical history as a starting point. A complete blood test may assist in diagnosis by identifying signs of infection. Various diagnostic tests may be required to confirm miliary tuberculosis, as outlined below.

Tuberculosis Test

A tuberculin test is performed by injecting a protein under the skin to observe the immune response. A positive result suggests prior exposure to tuberculosis, whether symptomatic or not. However, if the immune system is compromised, the test may yield a negative result even if active tuberculosis is present.

A sputum sample analysis may also be conducted, especially if the patient has a cough. The sample is examined for acid-fast bacilli (AFB) under a microscope, which helps detect tuberculosis bacteria.

Imaging Tests

Further imaging tests include chest x-rays, which can reveal characteristic spots on the lungs associated with miliary tuberculosis. A computed tomography (CT) scan may provide a more detailed image of the lung disease.

In well-equipped healthcare settings, a bronchoscopy may be performed. This procedure involves inserting a tube through the nose or mouth to view the airways and collect tissue samples for microscopic examination.

As miliary tuberculosis can affect multiple organs, additional tests may include:

• CT scans of different body areas, such as the intestines
• Magnetic resonance imaging (MRI) to detect infections in the brain and spinal cord
• Echocardiograms to assess infection in the fluid surrounding the heart
• Urine tests to detect bacterial presence
• Bone marrow biopsy using a specialized needle
• Biopsy of suspected infected tissue
• Lumbar puncture to check for brain infection
• Thoracentesis, which involves collecting fluid near the lungs to search for bacteria

Management

Treating miliary tuberculosis is similar to other forms of tuberculosis and involves a combination of antibiotics. Commonly used medications include rifampicin, isoniazid, pyrazinamide, and ethambutol. Injectable streptomycin may also be prescribed, and alternative antibiotics are used if tests indicate resistance to certain drugs.

Antibiotic treatment consists of two phases:

1. Intensive Phase

This phase focuses on rapidly reducing Mycobacterium tuberculosis levels. The prescribed drugs, usually rifampicin, isoniazid, pyrazinamide, ethambutol, and sometimes streptomycin, are taken daily for two consecutive months.

2. Continuation Phase

In this phase, the goal is to completely eliminate the tuberculosis bacteria. Medication can be administered daily or three times a week for four additional months. In cases of miliary tuberculosis, this phase may extend to 9–12 months.

To effectively combat miliary tuberculosis, patients must adhere to the prescribed medication schedule as directed by their physician. This treatment regimen demands strong commitment and adherence. Close contacts and healthcare providers often collaborate to assign a Medication Supervisor (PMO), who helps ensure the patient takes the medication at the correct dosage, on schedule, and without interruption.

The medications used to treat tuberculosis may lead to various side effects, ranging from mild to severe. Mild side effects may include:

• Red urine (harmless)
• Nausea

However, some side effects can be more serious, such as:

• Hepatitis (liver inflammation)
• Allergic reactions
• Neurological issues

If you encounter any side effects, consult your doctor regarding the continuation or adjustment of these medications. In addition to antibiotics, corticosteroids may be prescribed, especially if the infection impacts the brain or heart. In cases where an abscess forms, surgery may be necessary to prevent the infection from spreading.

Complications

Miliary tuberculosis is highly dangerous and can be fatal if treatment is delayed. Failure to treat this condition promptly can lead to severe complications, such as:

• Acute respiratory distress (extreme shortness of breath, potentially leading to respiratory failure)
• Multi-organ dysfunction
• Abnormal air presence in the chest, including:
• Pneumothorax (air between the lungs and chest wall)
• Pneumomediastinum (air in the mediastinal area containing the heart and blood vessels)
• Increased fluid around the heart and inflammation of the heart lining (pericarditis)
• Symptom exacerbation following HIV/AIDS medication (immune reconstitution inflammatory syndrome, IRIS)
• Heart muscle inflammation (myocarditis)
• Heart valve abnormalities
• Aortic dilation causing thinning of the arterial walls (aneurysm)
• Meningeal inflammation with specific neurological symptoms
• Kidney inflammation (glomerulonephritis)
• Decreased white blood cell count and widespread blood clotting (disseminated intravascular coagulation, DIC)

Prevention

Preventive measures for miliary tuberculosis include:

1. Bacillus Calmette-Guérin (BCG) Immunization

This vaccine is given to infants up to two months old, containing weakened tuberculosis bacteria that train the immune system to recognize and fight the bacteria. BCG is less effective when administered to children over two months old.

2. Tuberculosis Screening

Screening for symptoms allows for early identification, isolation, and management of tuberculosis cases, especially in individuals with weakened immune systems.

3. Managing Immune System Issues

For people with conditions like HIV/AIDS or diabetes, regular treatment is essential to maintain a strong immune system that can resist tuberculosis bacteria. For those on immunosuppressive medications, doctors may recommend antibiotics to help prevent miliary tuberculosis.

When to See a Doctor?

Individuals with a history of immune-compromising illnesses or medications should have routine checks for tuberculosis. Symptoms of miliary tuberculosis are similar to those of pulmonary tuberculosis but may affect other organs. Given the potential severity of untreated miliary tuberculosis, it is crucial to seek medical advice if you experience any related symptoms.

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