### Date : 2024-11-07 13:19 ### Topic : Miliary TB #pulmonology ---- **Miliary tuberculosis (TB)** is a rare and severe form of **disseminated TB** in which **Mycobacterium tuberculosis** bacteria spread through the bloodstream and create numerous small lesions throughout multiple organs. These tiny lesions resemble **millet seeds** on imaging, which is where the term "miliary" comes from. Miliary TB can affect multiple organs, including the lungs, liver, spleen, and central nervous system, and can be life-threatening without prompt treatment. ### Pathophysiology of Miliary TB Miliary TB occurs when TB bacteria enter the bloodstream (a process called **hematogenous dissemination**) and spread throughout the body: 1. **Primary Infection or Reactivation**: - Miliary TB can arise during an initial TB infection or from reactivation of latent TB when the immune system is compromised. - Once in the bloodstream, TB bacteria travel to distant organs, forming small, uniform granulomas. 2. **Formation of Granulomas**: - In each affected organ, immune cells form small nodules, or **granulomas**, around the bacteria in an attempt to contain them. - In miliary TB, these granulomas are numerous, small, and scattered throughout organs, appearing as tiny "millet-seed" spots on imaging. 3. **Multiorgan Involvement**: - The granulomas can compromise organ function, particularly when they accumulate in vital organs like the lungs, liver, and brain. Miliary TB in the lungs can impair oxygen exchange, while involvement in other organs can lead to organ-specific symptoms. ### Risk Factors for Miliary TB Certain groups are more susceptible to developing miliary TB: - **Immunocompromised Individuals**: People with weakened immune systems, such as those with HIV/AIDS, organ transplant recipients, or patients on immunosuppressive medications. - **Young Children and Elderly**: Both groups have less robust immune responses, making them more vulnerable to severe TB. - **Malnutrition**: Malnutrition weakens immune defenses, increasing the risk of TB reactivation and spread. - **People in High TB-Endemic Areas**: Prolonged exposure to TB in endemic areas increases the likelihood of infection. ### Symptoms of Miliary TB Miliary TB presents with systemic and organ-specific symptoms that vary depending on which organs are affected. Common symptoms include: - **Systemic Symptoms**: - **Fever** and **night sweats** - **Unintended weight loss** and **fatigue** - **Anorexia** (loss of appetite) - **Pulmonary Symptoms** (if the lungs are involved): - Persistent cough, shortness of breath, and occasionally hemoptysis (coughing up blood) - **Hepatic and Spleen Involvement**: - Hepatomegaly (enlarged liver), splenomegaly (enlarged spleen), jaundice, and abdominal pain. - **Central Nervous System Involvement**: - Headache, confusion, seizures, and in severe cases, TB meningitis. - **Other Organ Involvement**: - Bone pain if the skeletal system is involved, or lymphadenopathy (enlarged lymph nodes) if the lymphatic system is affected. ### Diagnosis of Miliary TB Diagnosing miliary TB can be challenging due to its nonspecific symptoms and the fact that it affects multiple organs. A combination of clinical, laboratory, and imaging studies are used to confirm the diagnosis: 1. **Imaging**: - **Chest X-ray**: May show a classic "miliary" pattern, with tiny, evenly distributed nodules (1-2 mm) throughout the lung fields. - **CT Scan**: More sensitive than an X-ray, providing detailed images of miliary nodules in the lungs and other affected organs. 2. **Laboratory Tests**: - **Sputum Analysis and Cultures**: Although sputum tests are useful for pulmonary TB, they may not always confirm miliary TB, as TB bacteria are often low in the sputum of these patients. - **Blood Cultures**: Mycobacterium tuberculosis can sometimes be detected in blood cultures, particularly in severely ill or immunocompromised patients. - **Liver Biopsy or Bone Marrow Biopsy**: These procedures may be performed if other tests are inconclusive. Histology shows granulomas, and cultures from these tissues can confirm TB. 3. **Tuberculin Skin Test (TST) or Interferon-Gamma Release Assay (IGRA)**: - TST and IGRA tests can indicate TB exposure but cannot distinguish miliary TB from other forms of TB. - In severely immunocompromised patients, these tests may be negative due to an impaired immune response (anergy). 4. **Elevated Serum Markers**: - **Elevated liver enzymes** may indicate liver involvement, while anemia, leukopenia, and thrombocytopenia may reflect bone marrow involvement. ### Treatment of Miliary TB The treatment of miliary TB involves a standard TB regimen, but it may require extended duration and close monitoring due to the complexity of the disease: 1. **Antitubercular Therapy (ATT)**: - Initial treatment typically includes **four first-line drugs**: **Isoniazid (INH)**, **Rifampin (RIF)**, **Pyrazinamide (PZA)**, and **Ethambutol (EMB)** for the first two months. - After the initial phase, isoniazid and rifampin are continued for an additional **4 to 10 months**, depending on the patient’s response and organ involvement. - Total treatment duration is often extended to **9-12 months**, especially for patients with central nervous system involvement. 2. **Corticosteroids**: - Corticosteroids may be used as adjunct therapy in cases with TB meningitis or significant lung inflammation to reduce swelling and prevent complications. 3. **Supportive Care**: - Patients with severe symptoms may require hospitalization for oxygen therapy, nutritional support, and other supportive measures. - Regular monitoring of liver function, kidney function, and visual acuity (for those on ethambutol) is essential to manage potential drug side effects. ### Complications of Miliary TB Miliary TB can lead to various complications, especially if not treated promptly: - **Respiratory Failure**: Widespread pulmonary involvement can impair oxygen exchange, leading to respiratory distress and failure. - **TB Meningitis**: Disseminated TB can involve the meninges, leading to meningitis, which is often life-threatening and associated with high morbidity. - **Organ Failure**: Extensive granuloma formation in the liver, kidneys, or spleen can lead to organ dysfunction and failure. - **Death**: Without treatment, miliary TB has a high mortality rate due to the rapid spread of bacteria and multiple organ involvement. ### Prognosis With prompt diagnosis and appropriate treatment, the prognosis for miliary TB can be good, but the outcome depends on factors like the patient’s immune status, organ involvement, and timeliness of treatment. In patients with compromised immune systems, such as those with HIV/AIDS, the prognosis is often poorer, and the risk of complications is higher. ### Summary - **Miliary TB**: A severe, disseminated form of TB where Mycobacterium tuberculosis spreads through the bloodstream to multiple organs. - **Symptoms**: Fever, night sweats, weight loss, and organ-specific symptoms, such as respiratory distress (lungs), jaundice (liver), and neurological symptoms (brain). - **Diagnosis**: Based on imaging (showing millet-like nodules), biopsy, cultures, and TB-specific tests (TST or IGRA). - **Treatment**: Long-term antitubercular therapy with the first-line TB drugs, often extended to 9-12 months, with possible corticosteroids for specific cases. Miliary TB requires early diagnosis and aggressive treatment to prevent complications, given its high potential for widespread organ damage and significant mortality if untreated. ### Reference: - ### Connected Documents: -