Author Archives: tcb6748

This week, a 75-year-old woman former smoker with history of recurrent PEs with abnormal CT imaging was presented. Her work up was notable for a +ANA (1:640) and an HP panel with low-level positive mold antibodies. A TTE showed normal LV and RV size and function with a mildly elevated RVSP. Her high-resolution chest CT had evidence of prominent mosaic attenuation, peripheral and peribronchovascular reticulations, ground glass, traction bronchiectasis, and extensive air trapping. Her PFTs normalized with a course of prednisone except for a persistent, mildly reduced DLCO. The patient had improvement in her cough and SOB but still had spells of lightheadedness. The question presented to the group was “Is there a need for further diagnostics for HP or pulmonary hypertension?”

I. What is mosaic attenuation?

Mosaic attenuation on CT is a heterogeneous pattern of attenuation that resembles…a mosaic.

This differing attenuation may represent:

(a) patchy interstitial disease

(b) diffuse ground glass disease (think acute pulmonary edema, viral/atypical pna, DAH)

(c) obliterative small airways disease

(d) occlusive vascular disease (aka “mosaic oligemia”)

(e) combination of any of the above

Differential for mosaic attenuation secondary to small airways disease:

In this patient, the presence of mosaic attenuation could represent either HP, mosaic oligemia from pulmonary vascular disease, or both.

II. Is there a way to differentiate between etiologies of mosaic attenuation radiologically?

• As mentioned by Dr Rishi Agrawal, one of the best ways to distinguish small airways disease from other forms of mosaic attenuation is by looking at your expiratory imaging on HRCT.
• In non-airways-related causes of mosaic attenuation, the lungs should increase in attenuation on expiratory imaging diffusely. This contrasts with what you should see in small-airways disease, where gas trapping will accentuate differences in attenuation.

III. Takeaways

• Mosaic attenuation is a non-specific finding on CT that can represent disease of the small airways, interstitium, alveoli, or pulmonary vasculature.
• In an undifferentiated patient, it is important to consider mosaic oligemia 2/2 PAH as a cause of mosaic attenuation.
• Pulmonary diseases affecting the small airways includes a broad differential (table above for reference).
• If the attenuation diffusely increases on expiration, it suggests that the etiology of the mosaic attenuation is NOT related to the small airways.

References:

Fleischner Society: Glossary of Terms for Thoracic Imaging https://doi-org.turing.library.northwestern.edu/10.1148/radiol.2462070712

Mosaic Attenuation: Etiology, Methods of Differentiation, and Pitfalls https://doi.org/10.1148/rg.2015140308

1. Necrobiotic rheumatoid nodules were discovered on biopsy in a patient with RA-ILD

What are the observed pulmonary manifestations of Rheumatoid arthritis?

Graingers and Allison’s Diagnostic Radiology, 9, 206-230.

What is epidemiology, clinical, radiologic, and pathologic criteria associated with necrobiotic rheumatoid nodules?

• Rare complication (1% with RA)
• More common in:
  • Men > Women
  • Long-standing disease
  • RF positivity
  • Active disease (esp cutaneous rheumatoid nodules’ also with joint disease, and elevated RA serologies)
• Morphology:
  • Single or multiple
  • mm to several cm in diameter
  • Well-circumscribed
  • May cavitate à leading to pneumothorax or bronchopleural fistula
  • May wax/wane
  • May be PET avid (although those >8 mm are not typically)
• Pulmonary nodules can paradoxically worsen with the start of RA therapy (most well observed with methotrexate)
• Nodules with upper/midzone predilection, located along interlobular septa or subpleural regions
• May cavitate (due to proteolytic enzymes) or rupture (leading to PTX or bronchopleural fistula)

European Respiratory Review 2015 24:1-16 (link)

Fishman’s Pulmonary Disease and Disorders, Chp 60, 5e.

In our case, a VATS biopsy was performed to rule out malignancy and infection as other causes of cavitating lung lesions.

2. Our second case featured a patient with history of Sjogren Syndrome (SS) with cystic lung disease. In this case, the mural thickening and nodularity of the cysts and presence of lymphadenopathy raised our concern for potential malignancy. Gabby Liu raised MALT lymphoma as a potential diagnosis.

What is the association between SS and MALT lymphoma?

• Among autoimmune disorders, SS is most strongly associated with the development of lymphoma
• In a small retrospective study describing biopsy-proven MALT lymphoma with lung involvement, 54% met criteria for SS

What are the commonly associated patterns of ILD in SS, and how are cystic lung diseases characterized and distinguished?

• Follicular bronchiolitis
• Lymphocytic interstitial pneumonia (LIP)
• Non-specific interstitial pneumonia (NSIP)
• Amyloidosis
• Lymphoproliferative disorders, including lymphoma

Clin Med Res. 2017; 15(1-2):6-12 (link)

AJRCCM 2015; 191(12) 1354-1666 (links 1 and 2 included below)

3. The third case involved a former smoker with CT findings of a probable UIP pattern with air trapping. The differential diagnosis included fibrotic hypersensitivity pneumonitis (fHP) vs IPF (i.e., CPFE). A bronchoscopy with BAL and lung biopsy were discussed as potential next steps for establishing diagnosis.

How is the diagnosis fHP arrived upon? How is fHP distinguished from other fibrotic ILDs?

AJRCCM 2020; 202(3):e36-e69. (link)