What is military tuberculosis?

Miliary Tuberculosis: Definition, Diagnosis, and Management

Miliary tuberculosis is a potentially lethal form of tuberculosis resulting from massive lymphohematogenous dissemination of Mycobacterium tuberculosis bacilli throughout the body, characterized by tiny millet seed-like lesions in multiple organs.

Definition and Pathophysiology

Miliary tuberculosis (MT) represents one of the most severe forms of tuberculosis infection. The term "miliary" refers to the characteristic appearance of multiple small nodules resembling millet seeds that are distributed throughout affected organs. This form results from:

• Massive lymphohematogenous dissemination of Mycobacterium tuberculosis
• Rupture of a tuberculous focus into blood vessels or lymphatic circulation
• Widespread seeding of bacilli throughout multiple organ systems

Epidemiology

Miliary tuberculosis is commonly found in:

• Children and young adults
• Immunocompromised individuals, particularly HIV-infected patients 1
• Persons with impaired cell-mediated immunity 2

Risk factors for progression to miliary TB include:

• Recent TB infection (within 1-7 years) 3
• HIV infection (35-162 cases per 1000 person-years) 3
• Injection drug use 3
• Silicosis 3
• Underweight status (>15% below standard weight) 3
• Diabetes mellitus 3
• Chronic renal failure requiring hemodialysis 3
• Immunosuppressive therapy (particularly corticosteroids) 3
• Organ transplantation 3
• Malignancies (especially lymphoma, leukemia) 3

Clinical Presentation

The clinical presentation of miliary TB is often non-specific and can be misleading:

• General symptoms predominate:
  • Fever
  • Night sweats
  • Weight loss
  • Fatigue
  • Anorexia
• Physical examination may be poor or unremarkable 1
• Clinical polymorphism makes diagnosis challenging 1
• Patients may present with:
  • Respiratory symptoms (cough, dyspnea)
  • Hepatosplenomegaly
  • Lymphadenopathy
  • Meningeal signs (if CNS involvement)
  • Skin lesions

Diagnosis

Diagnosing miliary TB is challenging due to:

1. Clinical polymorphism - varied presentation depending on organs involved
2. Lack of bacteriological proof in many cases 1
3. Atypical presentations such as:
   • Cryptic miliary tuberculosis
   • Acute respiratory distress syndrome 2

Diagnostic approaches include:

• Imaging:

  • Chest radiography showing classic "millet seed" pattern (may be absent early in disease)
  • CT scan for better visualization of lesions

• Microbiological confirmation:

  • Isolation of M. tuberculosis from sputum, body fluids, or biopsy specimens
  • Molecular methods such as PCR 2

• Histopathological examination:

  • Tissue biopsy showing caseating granulomas
  • Demonstration of acid-fast bacilli

• Laboratory findings:

  • Anemia
  • Leukopenia or leukocytosis
  • Elevated liver enzymes
  • Hyponatremia
  • Pulmonary function and gas exchange impairment 2

Treatment

Without treatment, miliary tuberculosis is fatal 1. Treatment principles include:

1. Standard first-line antituberculosis drugs:

   • Isoniazid
   • Rifampin
   • Ethambutol
   • Pyrazinamide

2. Treatment duration:

   • Generally 6 months or longer depending on clinical response
   • May require extended therapy for CNS involvement

3. Supportive care:

   • Nutritional support
   • Management of complications
   • Treatment of underlying conditions

4. Monitoring:

   • Regular clinical assessment
   • Laboratory monitoring for drug toxicity
   • Evaluation of treatment response

Prognosis

The prognosis of miliary tuberculosis depends on:

• Early diagnosis and prompt initiation of treatment 1
• Extent of organ involvement
• Presence of complications
• Immune status of the patient

Prevention

Prevention strategies include:

• Early identification and treatment of latent TB infection
• TB screening for high-risk populations
• Infection control measures in healthcare settings 3
• Comprehensive person-centered care addressing risk factors like undernourishment, smoking, and alcohol use 4

Special Considerations

For military personnel and others at risk due to congregate living or deployment to endemic areas:

• TB control activities should focus on mitigating unique exposures 5
• Screening for latent TB infection before deployment
• Monitoring for TB disease during and after deployment to endemic areas

Early diagnosis and prompt treatment are critical to improving outcomes in this potentially lethal form of tuberculosis.