Biology and Diagnosis of CPFE

Combined Pulmonary Fibrosis and Emphysema (CPFE) is a unique syndrome where two different types of lung damage occur at the same time. While they may seem like opposites, their biology is deeply linked, and understanding how they interact is key to your diagnosis and care plan.

What Causes CPFE?

The most significant risk factor for CPFE is a long history of cigarette smoking ^[1]. Smoking can trigger two different pathways of damage: oxidative stress that destroys the air sacs (emphysema) and abnormal inflammation that leads to scarring (fibrosis) ^[2]. While most common in men with a history of heavy smoking, CPFE can also be caused by other factors:

• Occupational Exposures: Breathing in dust or fumes from coal, welding, or agrochemicals can trigger the same patterns of damage ^[3].
• Autoimmune Disease: Some people develop CPFE as part of a connective tissue disease (CTD), such as Rheumatoid Arthritis or Systemic Sclerosis ^[4][5].
• Genetic Factors: Researchers have identified certain genetic markers that may make some people more susceptible to developing both conditions simultaneously ^[6][7].

The Key Imaging Test: HRCT

Because your symptoms and basic breathing tests can be misleading, doctors rely on High-Resolution Computed Tomography (HRCT) to identify CPFE and its components ^[8]. This detailed imaging looks for a “classic” visual pattern:

1. Upper-Zone Emphysema: Areas at the top of the lungs where the air sacs are enlarged and damaged ^[9].
2. Lower-Zone Fibrosis: Areas at the bottom of the lungs where the tissue is thick, scarred, and often has a “honeycomb” appearance ^[8].

While this top-and-bottom distribution is common, specialists often find that the two conditions overlap and coexist within the same areas of the lung, and the fibrosis may not always have honeycombing ^[9].

Why Spirometry Can Be “Less Abnormal Than Expected”

One of the most biologically fascinating parts of CPFE is why your spirometry (a test of how much and how fast you can breathe) may look normal. This is a phenomenon known as “pseudo-normalization” ^[10].

• The Balancing Act: Fibrosis makes lungs stiff and small, which would normally show a low FVC (Forced Vital Capacity). Emphysema makes lungs extra-stretchy and large. When you have both, they can offset each other on volume tests, making your lung size look less abnormal than expected ^[8][10].
• Traction Support: Scarred tissue from fibrosis can physically pull your airways open (tractional dilation), a consequence of remodeling that alters breathing test results ^[11].

Because of this, doctors place the most weight on your DLCO test (Diffusion Capacity), which uses carbon monoxide as a proxy to estimate gas transfer. This score is often disproportionately reduced in CPFE because both conditions have destroyed the surface area where oxygen enters your blood (though it can also be affected by anemia and other factors) ^[10][12].

Identifying the Fibrosis Pattern

Not all CPFE is the same. Once CPFE is identified, your specialist must determine the pattern and underlying cause of the fibrosis involved. This is crucial because it helps guide your treatment:

• IPF: If the fibrosis follows a UIP (Usual Interstitial Pneumonia) pattern and has no other known cause, it is diagnosed as Idiopathic Pulmonary Fibrosis (IPF). This often involves antifibrotic medications like nintedanib or pirfenidone, depending on local approvals ^[13][14].
• CTD Subtype: If the fibrosis is linked to an autoimmune disease, the focus may be on immunosuppressant medications to calm the overactive immune system ^[15].
• Other/Unclassifiable: In some cases, the pattern doesn’t fit a standard category. Your team will monitor these cases closely for a progressive phenotype (signs that the scarring is worsening over time), which may then qualify for specific antifibrotic treatments ^[16].

A Quick Glossary of Terms

• FVC (Forced Vital Capacity): The total amount of air you can forcefully exhale.
• DLCO (Diffusion Capacity): A test estimating how well your lungs transfer gas into your blood.
• HRCT / LDCT: High-Resolution CT is for detailed lung diagnosis. Low-Dose CT is used for lung cancer screening.