06/17/2026
Day 1: What Is Autoimmune Disease and How Does It Develop?
Before we can understand diseases like perianal fistulas, lupus, immune-mediated polyarthritis, or autoimmune thyroid disease, we first need to understand what autoimmune disease actually is.
The immune system is designed to protect the body. Its job is to identify threats such as bacteria, viruses, parasites, and abnormal cells and eliminate them before they cause harm.
In a healthy dog, the immune system can tell the difference between “self” and “foreign invaders.”
In a dog with an autoimmune disease, that recognition system breaks down.
The immune system mistakenly identifies the body’s own tissues as a threat and launches an attack against them.
Depending on which tissues are targeted, the disease can affect different parts of the body:
🐾 Skin
🐾 Joints
🐾 Digestive tract
🐾 Thyroid gland
🐾 Blood cells
🐾 Nervous system
🐾 A**l and re**al tissues, as seen with perianal fistulas
Researchers still do not know every reason why autoimmune diseases develop, but studies suggest they occur when several factors come together:
• Genetic predisposition
• Immune system dysregulation
• Environmental influences
• Chronic inflammation
• Changes in the gut microbiome
Research has shown that certain breeds, including German Shepherds, are genetically predisposed to several immune-mediated conditions. Scientists believe specific genes involved in immune regulation may increase susceptibility to disease.
One of the most important discoveries in recent years is the connection between the gut and the immune system.
Approximately 70% of the immune system is associated with the gastrointestinal tract. The gut microbiome helps train and regulate immune responses. When the microbiome becomes imbalanced, immune function can also become disrupted.
Studies have found significant differences in gut microbial populations between healthy dogs and dogs suffering from chronic inflammatory and immune-mediated conditions.
This does not mean gut health alone causes autoimmune disease.
It means autoimmune disease is likely influenced by a combination of genetics, immune dysfunction, environmental exposures, inflammation, and gut health.
For dogs like Max, the result was a body that began attacking itself.
For seven years, Max battled perianal fistulas—one of the most painful immune-mediated diseases seen in dogs. What started deep within the immune system eventually showed up as painful lesions around his a**s that affected his comfort, mobility, and quality of life. He would lick them to the point of bleeding when they were flared up. He didn’t have to live like this his entire life though. We will cover the steps to take and what to do to help alleviate the pain and to reduce the fistulas in this series.
When we understand what is happening inside the body, we can make more informed decisions, ask better questions, and become stronger advocates for the dogs who depend on us.
Tomorrow, we’ll dive deeper into perianal fistulas—what they are, why they develop, and why German Shepherds like Max are at greater risk.
