Miliary Pattern



Miliary Pattern


Jeffrey P. Kanne, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Mycobacterial


  • Metastases


  • Viral Pneumonia


  • Disseminated Fungal Disease


Less Common



  • Sarcoidosis


  • Silicosis/Coal Worker’s Pneumoconiosis


  • Talcosis


  • Alveolar Microlithiasis


  • Lung Ossification


  • Bronchioloalveolar Cell Carcinoma


Rare but Important



  • Intravesical Bacillus Calmette-Guérin (BCG) Immunotherapy


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Definition: Diffuse tiny lung nodules (< 5 mm in diameter)



    • Determine location of nodules with respect to secondary pulmonary lobule



      • Centrilobular or perilymphatic or random


    • Term “miliary” derived from Latin; related to millet seed, which it resembles


  • Miliary pattern: Random pattern



    • Random distribution of nodules in secondary pulmonary lobule


    • Too numerous to count, < 5 mm in diameter


    • Pathophysiology: Random miliary pattern primarily due to hematogenous spread of disease


  • Chest radiographs vs. HRCT



    • Chest radiograph may be normal even in biopsy-proven cases



      • Summation effect on radiograph: Superimposition of nodules otherwise below detection threshold allows detection


      • Sensitivity of chest radiographs in miliary tuberculosis: 60-70%


    • HRCT more sensitive than chest radiographs


Helpful Clues for Common Diagnoses



  • Mycobacterial



    • Tuberculosis



      • Miliary spread may occur during primary or post-primary stages, usually with severe immunosuppression


      • Presentation in HIV depends on severity of immunosuppression: Miliary presentation usually occurs when CD4(+) < 200


      • Sputum often AFB negative; bronchoscopy with transbronchial biopsy or liver or bone marrow biopsy often necessary for diagnosis


      • Spectrum of illness: Asymptomatic to severe respiratory distress


    • Nontuberculous mycobacteria



      • Usually centrilobular nodules


      • Miliary pattern occasionally seen in immunocompromised hosts


      • May be associated with bronchiectasis


  • Metastases



    • Most frequently seen with



      • Melanoma


      • Thyroid carcinoma


      • Choriocarcinoma


      • Renal cell carcinoma


    • Miliary metastases typically larger than those of tuberculosis


    • Tend to have more well-defined margins than miliary tuberculosis


    • Background ground-glass attenuation more common with miliary tuberculosis


    • Chronic miliary tuberculosis nodules usually more profuse in upper lung zones whereas metastases more common in lower lung zones


  • Viral Pneumonia



    • Varicella (chickenpox)



      • Healed varicella pneumonia can present as miliary calcified nodules


    • Influenza



      • Miliary pattern rare but has been described; also seen in other viral infections, such as Cytomegalovirus


  • Disseminated Fungal Disease



    • Usually occurs in those with impaired T-cell immunity, elderly, or debilitated


    • Pattern identical to miliary tuberculosis


    • Upper lung zone proclivity seen with blastomycosis; uncommon with other fungi


    • May progress to diffuse lung consolidation



    • May complicate acute or chronic disease or be initial manifestation


Helpful Clues for Less Common Diagnoses



  • Sarcoidosis



    • Usually nodules in a perilymphatic distribution, rarely miliary


    • Mid and upper zone predominance


    • May have symmetric hilar and mediastinal lymphadenopathy


  • Silicosis/Coal Worker’s Pneumoconiosis



    • Usually nodules in a perilymphatic distribution, rarely miliary


    • Occupational exposures essential


    • Tuberculosis can complicate both silicosis and coal worker’s pneumoconiosis


    • May have symmetric hilar and mediastinal lymphadenopathy


  • Talcosis



    • Talc: Common ingredient in oral medication ground-up with intent to inject intravenously


    • Initial miliary pattern may coalesce to progressive massive fibrosis, much like silicosis


    • Findings of pulmonary hypertension may be present


  • Alveolar Microlithiasis



    • Calcification of nodules striking


    • Subpleural sparing results in “black pleura” sign


  • Lung Ossification



    • Densely calcified, 1-5 mm nodules concentrated in middle and lower lungs


    • Associated with chronic severe mitral stenosis


    • Idiopathic form also exists, associated with pulmonary fibrosis


    • Tend to become confluent and may form osseous trabeculae (3-13%)


    • Tends not to be severe; miliary pattern uncommon


    • Typically patients are elderly and male; symptoms uncommon


  • Bronchioloalveolar Cell Carcinoma

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Aug 8, 2016 | Posted by in CARDIOLOGY | Comments Off on Miliary Pattern

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