This x-ray shows a bilateral diffuse miliary nodular pattern involving both lung fields with no loss of volume. Characteristically, miliary nodules are less than 4 mm in size. They are generally noncalcified and diffuse and are seen in many conditions, such as TB/fungal infections/pneumoconiosis and ceain malignancies such as melanomas/thyroid cancer. Larger, more confluent lesions can be seen in alveolar sarcoid, Wegener's granulomatosis, and metastatic disease. The clinical hints that aid diagnosis include: An occupational history without constitutional symptoms. X-ray that looks worse than the patient's complaints, as in sarcoidosis. History of thromboembolic disease or sepsis, as in septic emboli or pulmonary infarcts. These are generally seen in the lower lung zones. * History of ahritis; may suggest rheumatoid nodules. Presence of eosinophilia in the peripheral smear with fleeting infiltrates; provides clue for pulmonary infiltrates with eosinophilia (PIE) syndrome, in which case history of travel or use of medications/drugs may be helpful and a stool exam may aid in the diagnosis. Immune-compromised patients may have oppounistic infections such as herpes or CMV This elderly patient has all the stigmata of chronic illness. Although the PPD skin test and sputum studies are negative (seen in about 30% of cases), the history and CXR are consistent with miliary TB. Hyponatremia and hypercalcemia are common findings in TB. In this age group sarcoidosis is unlikely. In the absence of occupational exposure, silicosis is also unlikely. Bone marrow aspirate may be positive for TB culture in 60% of patients with miliary TB, and aspiration is a logical step in the diagnostic evaluation. CT scan will not aid fuher in the diagnosis, and thyroid function tests will be normal unless there is clinical evidence of hypo- or hypehyroidism. Open lung or thoracoscopic biopsy is always diagnostic.