Miliary micronodular shadows in the lungs.
Both our cases had a similar radiographic presentation of miliary micronodular shadows.
This pattern of large number of similar-sized micronodules which are seen in both lungs is called miliary. The resemblence to millet seeds (from which the term miliary is derived) is typical of this pattern of lesions.
Their distribution usually reflects lung perfusion, since most of them are embolic. They can have infectious (specially mycobacteria and some fungi), neoplastic, or foreign material (talc) causes. In tuberculosis the originating process
is classically supposed to erode into the draining veins of a bronchus
and then distributed to the lungs in showers of bacteria.
In some cases the pathogenesis is inhalatory: fungi, silicosis or talcosis.
In another group of patients the pathogenesis is unknown: sarcoidosis, Langerhans cells granulomatosis, Wegener's granulomatosis.
Miliary micronodular pattern has an extensive list of differential diagnoses. The George Simon's Chest X-ray collection has many cases of micronodular shadows, starting with miliary tuberculosis:
http://www.sbu.ac.uk/~dirt/museum/gs-fifth.html
In almost all of them Bronchoalveolar lavage is a very useful diagnostic tool.
The WebPath teaching collection of surgical pathology material should be used in conjunction with the X-Ray teaching file in order to master the pathology-radiology correlation:
http://www-medlib.med.utah.edu/WebPath/LUNGHTML/LUNGIDX.html
Interesting eMedicine article on Miliary tuberculosis.