Diffuse Cystic Lung Disease: CT Pattern Recognition and Differential Diagnosis
A practical radiology review of Diffuse Cystic Lung Disease: CT Pattern Recognition and Differential Diagnosis, focused on imaging findings, differential diagnosis, reporting...
A practical radiology review of Diffuse Cystic Lung Disease: CT Pattern Recognition and Differential Diagnosis, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.
Definition
- 4 cysts abnormal, >10 cysts = multicystic DCLD
- Cyst = round lucency + thin wall ≤2 mm
Always exclude mimics first
- Emphysema
- Honeycombing
- Cavities
- Cystic bronchiectasis
Big 4 DCLDs You Must Know
Lymphangioleiomyomatosis (LAM)
- Female-predominant | mTOR pathway | TSC-related
CT
- Diffuse, bilateral, uniform, round cysts
- No zonal predominance
- Normal intervening parenchyma
- ± chylothorax
- ± renal AML
- Dx clues
- ↑ VEGF-D ≥800 pg/mL
- Associated Tuberous sclerosis complex
- Renal angiomyolipoma
- Complications
- Recurrent pneumothorax
- Progressive respiratory failure
- Tx
- mTOR inhibitor (sirolimus)
- Early pleurodesis
- Transplant (good outcomes)
Birt-Hogg-Dubé syndrome (BHD)
- AD inheritance | FLCN mutation | No gender predilection
CT
- Basal + subpleural predominance
- Elliptical/lentiform cysts
- Perivascular, paramediastinal
Clinical clues
- Recurrent pneumothorax
- Skin fibrofolliculomas
- family history
- Major risk
- Renal tumors (bilateral, multifocal)
Rad pearl
- Renal MRI surveillance required
Pulmonary Langerhans cell histiocytosis (PLCH)
- 90% smokers | MAPK mutations
- CT evolution
- Nodules
- Thick-walled cavities
- Irregular/bizarre cysts
- Distribution
- ⬆ Upper & mid lung predominance
- Spares costophrenic angles
- Pneumothorax (15–20%)
- Pulmonary HTN (late)
- Tx
- Smoking cessation = key
- BRAF/MEK inhibitors (progressive)
Lymphoid interstitial pneumonia (LIP) / FB
- Female > male | Autoimmune association
CT
- Thin-walled cysts (1–30 mm)
- Lower lobe predominance
- Perivascular
- Ground-glass / nodules
- Think of
- Sjögren syndrome
RA / SLE
CVID / HIV
- Progressive impairment
- Rare lymphoma transformation
- Tx
Treat underlying autoimmune disease
- Systematic CT Approach
1. Confirm true cyst
2. Exclude mimics
3. Count cysts (paucicystic vs multicystic)
4. Assess
- Distribution
- Shape
- Size variability
- Wall thickness
- Nodules? GGO? Effusion?
- Renal findings?
Pneumothorax & Lifestyle Pearls
- High recurrence in LAM, BHD, PLCH
- Pleurodesis after first episode
- Air travel generally safe (~1% risk)
- Avoid scuba diving
- Smoking cessation critical
Final Takeaway
If you see
- diffuse uniform cysts → LAM
- Basal elliptical cysts + skin/renal → BHD
- Upper lobe bizarre cysts → PLCH
- autoimmune + GGO + perivascular cysts → LIP
Clinical use note
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