Miliary tuberculosis

Miliary tuberculosis is a form of tuberculosis, characterized by a wide dissemination into the human body, with small lesions looking like millet seeds (1–5mm). Its name comes from a distinctive pattern seen on a chest radiograph 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.

Signs and symptoms

Patients with miliary tuberculosis often experience non-specific signs, such as coughing and enlarged lymph nodes. Miliary tuberculosis can also present with enlarged liver (40% of cases), enlarged spleen (15%), inflammation of the pancreas (<5%), and multiple organ dysfunction with adrenal insufficiency (adrenal glands do not produce enough steroid hormones to regulate organ function).

Other symptoms include fever, hypercalcemia, choroidal tubercles, and cutaneous lesions. Firstly, many patients can experience a fever lasting several weeks with daily spikes in morning temperatures.

Secondly, hypercalcemia has been reported in approximately 16–51% of patients with tuberculosis. This phenomenon may result from increased macrophage activity in the body, whereby activated macrophages produce excess 1,25-dihydroxycholecalciferol (calcitriol). Calcitriol enhances the ability of macrophages to kill bacteria; however, elevated levels of calcitriol increase intestinal calcium absorption, which can lead to hypercalcemia in some cases. Additionally, hypercalcemia has been identified as a notable clinical feature of miliary tuberculosis.

Thirdly, chorodial tubercules, pale lesions on the optic nerve, typically indicate miliary tuberculosis in children. These lesions may occur in one eye or both; the number of lesions varies between patients. Chorodial tubercules may serve as important symptoms of miliary tuberculosis, since their presence can often confirm suspected diagnosis.

Lastly, 10–30% of adults and 20–40% of children with miliary tuberculosis have tuberculosis meningitis.

The risk factors for contracting miliary tuberculosis are being in direct contact with a person who has it, living in unsanitary conditions, and poor nutrition. In the U.S., risk factors for contracting the disease include homelessness and HIV/AIDS.

Cause

Miliary tuberculosis is a form of tuberculosis that is the result of Mycobacterium tuberculosis travelling to extrapulmonary organs, such as the liver, spleen and kidneys. Although it is well understood that the bacteria spread from the pulmonary system to the lymphatic system and eventually the blood stream, the mechanism by which this occurs is not well understood.

One proposed mechanism is that tuberculous infection in the lungs results in erosion of the epithelial layer of alveolar cells and the spread of infection into a pulmonary vein. Once the bacteria reach the left side of the heart and enter the systemic circulation, they may multiply and infect extrapulmonary organs.

Alternatively, the bacteria may attack the cells lining the alveoli and enter the lymph node(s).

The tuberculin skin test, commonly used for detection of other forms of tuberculosis, is not useful in the detection of miliary tuberculosis. The tuberculin skin test fails due to the high numbers of false negatives. These false negatives may occur because of higher rates of tuberculin anergy compared to other forms of tuberculosis. "Common medication side effects a patient may have such as inflammation of the liver if a patient is taking pyrazinamide, rifampin, and isoniazid. A patient may also have drug resistance to medication, relapse, respiratory failure, and acute respiratory distress syndrome."

Miliary tuberculosis

Signs and symptoms

Cause

See also

References

Further reading

External links