What Are the Types of Fibrosis?

Fibrosis can develop on any tissue in the body but most commonly affects the lungs and skin. Several types of fibrosis can develop, depending on what's causing it.

Learn more about types of fibrosis, their causes, and risk factors.

What Is Fibrosis?

The term "fibrosis" is used to describe tissue that has overgrown, hardened, and/or scarred as a result of chronic inflammatory processes. Unlike acute inflammation, chronic inflammation lasts for months.

The processes of inflammation, tissue remodeling, and repair co-occur, creating an excess of extracellular matrix (space outside of cells in connective tissue) components, such as collagen, which causes tissues to overgrow, harden, and scar.

Several conditions can generate chronic inflammatory reactions, such as persistent infections, autoimmune reactions, allergic responses, chemical insults, radiation, and tissue injury.

Types 

While fibrosis can occur in any of the body's tissues, some types are more prevalent than others.

Lung

Pulmonary fibrosis causes scarring within the lung tissue, often with no known cause. There are several subtypes of pulmonary fibrosis. These include:

• Idiopathic pulmonary fibrosis (IPF) is the most common type of pulmonary fibrosis. "Idiopathic" means there is no known cause. Approximately 50,000 new cases of IPF are diagnosed annually, with most people noticing symptoms between the ages of 50 and 70. IPF tends to be more common in men, although more women are getting diagnosed.
• Disease-related pulmonary fibrosis results from disease processes. Autoimmune diseases, such as rheumatoid arthritis or scleroderma (chronic autoimmune disease affecting connective tissue), and some viral illnesses can cause chronic inflammation, which can result in fibrosis in the lung tissues. Gastroesophageal reflux disease (GERD) can also cause fibrosis as stomach acid backs up and gets potentially inhaled into the lungs, damaging the tissues.
• Familial pulmonary fibrosis may occur if IPF or idiopathic interstitial pneumonia (IIP) runs in families (specifically, if it's diagnosed in two or more family members). While the condition is rare, discuss your risk for this type of fibrosis with your healthcare provider.
• Exposure-related pulmonary fibrosis can occur from hazardous materials, such as asbestos or silica. Other exposures, such as radiation treatments, smoke inhalation, and cigarette smoking, can also increase the risk of developing pulmonary fibrosis. 
  

Skin

As with most pulmonary fibrosis cases, the underlying cause of skin fibrosis is not well understood. Skin fibrosis is usually the result of one of the following:

• Autoimmune diseases: Scleroderma is the primary autoimmune disease that causes skin fibrosis. Raynaud's phenomenon (a condition that leads to the constriction of small blood vessels in the hands or feet) also contributes to it.
• Trauma: Extensive trauma, like radiation therapy to treat cancer, can create an environment for skin fibrosis to develop.
• Disease processes: Skin-specific disease processes, such as graft-versus-host disease, can also trigger a chronic inflammatory state, leading to skin fibrosis.
  

Other Types of Fibrosis

Although lung and skin fibrosis are more common, fibrosis can occur in any tissue in the body. Other types of fibrosis include:

• Cardiac: Different heart diseases, including myocardial infarction (heart attack), heart failure, and diabetic heart disease, can cause heart tissue to develop fibrosis.
• Kidney: Chronic kidney disease, trauma, or autoimmune diseases, like lupus, can contribute to the development of kidney fibrosis.
• Liver: Viruses like hepatitis or chronic metabolic liver disease like cirrhosis can cause fibrosis to develop in the liver.
  

General Symptoms and Effects of Scar Tissue 

Although different types of fibrosis affect various body systems and organs, there are some general commonalities among the fibrotic conditions, including:

• Fibrous tissue cannot perform the same functions as healthy tissue.
• As fibrotic tissue accumulates, it impairs the ability of the organ or body system to function and can ultimately lead to organ or body system failure.
  

Causes

Fibrosis is a result of an underlying disease or trauma. Often, the cause of the fibrosis is not known.

Risk Factors 

The actual cause of most fibrosis is not known or well understood. Since disease processes, trauma, and other unknown causes are the underlying reason preceding the fibrosis process, some considerations can be taken to prevent fibrosis, such as:

• While most pulmonary fibrosis stems from unknown causes, some cases are linked to exposure to cigarette smoke or hazardous chemicals. Avoiding smoke and using respiratory protective equipment when working with dangerous chemicals can limit exposure and prevent fibrosis.
• Cardiac fibrosis often results from a disease process affecting the heart. Heart disease risk factors include a poor diet, a sedentary lifestyle, obesity, and/or tobacco use. Lifestyle modifications to avoid those risk factors can prevent heart disease and cardiac fibrosis.
• Liver fibrosis is often the result of cirrhosis. Cirrhosis is most often linked to excessive alcohol usage, so limiting alcohol intake can prevent liver fibrosis.

Summary

Fibrotic tissue is tissue that has overgrown, hardened, or scarred as a result of chronic inflammatory processes. The majority of fibrosis cases stems from unknown causes. Fibrosis can affect any tissue or organ; the most common tissues and organs affected are the skin and lungs, but it can also affect the heart, kidney, or liver.