Miliary tuberculosis

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Overview
Miliary tuberculosis (or disseminated TB) is a form of tuberculosis that is characterized by a wide dissemination into the human body and by the tiny size of the lesions (1-5 mm). Its name comes from a distinctive pattern seen on a chest X-ray of many tiny spots distributed throughout the lung fields with the appearance similar to millet seeds, thus the term "miliary" tuberculosis. Miliary TB may infect any number of organs including the lungs, liver, and spleen. It is a complication of 1-3% of all TB cases.

Differential Diagnosis of Miliary Pattern on chest X-ray

 * Miliary tuberculosis
 * Varicella pneumonia
 * Acute hypersensitivity pneumonitis
 * Fungal pneumonia
 * Thyroid cancer metastases
 * Renal cell carcinoma metastases

Etiology
Miliary tuberculosis is a form of tuberculous infection in the lung that is the result of erosion of the infection into a pulmonary vein. Once the bacteria reach the left side of the heart and enter the systemic circulation, the result may be to seed organs such as the liver and spleen with said infection. Alternately the bacteria may enter the lymph node(s), drain into a systemic vein and eventually reach the right side of the heart. From the right side of the heart, the bacteria may seed - or re-seed as the case may be - the lungs, causing the eponymous "miliary" appearance.

Signs and Symptoms
A patient with miliary tuberculosis will tend to present with non-specific signs such as low grade fever, cough, and generalized lymphadenopathy. Miliary tuberculosis can also present with hepatomegaly (40% of cases), splenomegaly (15%), pancreatitis (<5%), and multiorgan dysfunction with adrenal insufficiency.

Diagnostic Findings
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Treatment

 * See: Tuberculosis treatment

Miliary TB is a serious condition; untreated miliary TB is almost always fatal. About 25% of patients with miliary TB also have tuberculous meningitis. The standard treatment recommended by the WHO is with isoniazid and rifampicin for six months, as well as ethambutol and pyrazinamide for the first two months. If there is evidence of meningitis, then treatment is extended to twelve months. The US guidelines recommend nine months' treatment.