Miliary tuberculosis. Frontal X-ray of a section through the chest of a 30-year-old male patient with miliary tuberculosis (TB), showing very thin micronodules uniformly distributed in the lung tissue. TB is caused by infection with Mycobacterium tuberculosis bacteria. Miliary (or disseminated) tuberculosis is a form of tuberculosis characterised by a wide dissemination into the human body and by the tiny size of the lesions (1-5 mm) seen n the lung tissue. Its name derives from the distinctive pattern seen on a chest X-ray such as this one, with many tiny spots distributed throughout the lung fields with the appearance similar to millet seeds; thus the term miliary tuberculosis.