<s>[INST] context: 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. [/INST] question: A 71-year-old man is seen with low-grade fever, generalized malaise, and a run-down feeling. He has lost weight and shows stigmata of chronic illness. There is no history of occupational exposure. On physical examination, vital signs are as follows: pulse 110 bpm; temperature 99degF; respirations 19/min; blood pressure 90/60 mm Hg. On exam, the man is frail and appears cachectic with temporal wasting. Other aspects of his physical exam are unremarkable. Laboratory data: Hb 10 g/dL; Hct 30%; MCV 90; WBCs 3000/uL; differential normal; BUN 19 mg/dL; creatinine 1.0 mg/dL; sodium 129 mEq/L; potassium 5.0 mEq/L; ABGs (RA): pH 7.42, PCO2 35 mm Hg, PO2 58 mm Hg. Spirometry: FVC 60% of predicted; FEV1 60% of predicted. PPD skin test is negative (0 mm); induced sputum for AFB smear is negative. Chest radiograph is shown below.What is the most likely diagnosis? | options: A: Silicosis B: Miliary TB C: Metastatic thyroid carcinoma D: Sarcoidosis | answer: B </s>