May 12, 2026, 7:35 pm | Read time: 9 minutes
At first, it often begins unremarkably. A bit tired, a tugging in the stomach, dry eyes, maybe a rash that won’t go away. None of this seems truly threatening or intimidating. What many don’t know: It’s an attack from within. It’s not a virus or bacteria, but the body’s own immune system. In an autoimmune disease, the immune system can no longer distinguish between the body’s own and foreign structures, and instead turns against itself.
What Is an Autoimmune Disease?
The immune system is one of the body’s most complex defense systems. It identifies invaders like viruses or bacteria and ensures they don’t make us sick. At the same time, it has an internal filter: It knows what belongs to the body and doesn’t attack these structures.
This mechanism becomes unbalanced in an autoimmune disease. The distinction between “self” and “foreign” no longer works reliably. The body then classifies its own tissue as a threat and initiates a defense reaction.
The name itself describes what happens: An autoimmune disease is called so because the immune system turns against the body–”auto” comes from Greek and means “self.”
This leads to the formation of so-called autoantibodies. These specifically target the body’s own cells. The result is inflammation that doesn’t subside but persists or recurs. This also explains why an autoimmune disease is considered chronic. It often accompanies those affected for many years.1
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Many Clues–but Rarely a Clear Picture
The symptoms of an autoimmune disease are as varied as the diseases themselves. This makes it difficult to recognize them early. Depending on which organ is affected, very different complaints can appear. Skin rashes, joint pain, or digestive tract issues are common. Abdominal pain, diarrhea, fever, or muscle pain can also occur.
Some people report dry eyes or mouth, others blood in stool or urine. What many autoimmune diseases have in common are chronic inflammations. These can manifest as pain, redness, swelling, or a feeling of warmth.2
There are also nonspecific symptoms like fatigue, exhaustion, or reduced performance. These are often underestimated or attributed to other causes for a long time. A typical feature is the episodic course. Symptoms appear more intensely in phases, subside, and can reappear later. Each autoimmune disease develops individually.
Why the Immune System Suddenly Reacts Incorrectly
The causes of an autoimmune disease are still not fully understood. There isn’t a single trigger, but rather an interplay of several factors. Genetic predisposition can play a role. Autoimmune diseases occur more frequently in some families.3
External influences like infections, hormonal changes, or environmental factors also play a role. Stress or certain medications can affect the immune system.
One possible mechanism is the so-called “cross-reaction.” Here, pathogens resemble the body’s own tissue. The immune system then reacts not only to the pathogen but also attacks the body. Why this misdirection occurs in some people and not others remains unclear.4
Two Forms: Localized or Throughout the Body
Autoimmune diseases can be broadly divided into two forms:
- In organ-specific diseases, the immune reaction targets a single organ. This can be, for example, the thyroid or pancreas.
- In systemic autoimmune diseases, multiple organs or tissues are affected. Inflammations can occur in various parts of the body.5
In practice, there are also transitional forms that cannot be clearly categorized.
Which Organs Can Be Affected–and Why It’s So Important
As mentioned, autoimmune diseases don’t have a fixed “target organ.” They can occur in very different parts of the body–and that’s what makes them so difficult to classify.
Thyroid
The thyroid is particularly often affected. It reacts sensitively to immune system misdirection. This can alter hormone production–either slowed down or increased. For those affected, this often means nonspecific symptoms like fatigue, weight fluctuations, or inner restlessness–things that initially don’t seem clear.
Skin
The skin is also among the organs that frequently react. It’s visible, and that’s why something is often noticed here first. Inflammatory processes can manifest as redness, scaling, or other changes. However, not every skin change is immediately recognized as part of an autoimmune disease.
Intestine
The intestine is another central site for autoimmune processes. The intestinal lining is attacked, resulting in symptoms like diarrhea, abdominal pain, or impaired nutrient absorption. Here, too, the connection isn’t always immediately clear, as many of these symptoms can have other causes.
Internal Organs
Less obvious but equally important are organs like the liver, kidneys, or adrenal glands. Processes occur here in secret, making diagnosis even more difficult.
Nervous System
The nervous system is one of the most sensitive areas. When structures here are attacked, it can have very different consequences–from vision problems to numbness to movement issues.
Eyes
Even the eyes can be affected. Inflammations or dry eyes show that even small, specialized structures can become targets of the immune system.
Systemic Forms: When the Whole Body Reacts
Finally, there are systemic forms where not just a single organ is affected. The inflammation can occur simultaneously in multiple parts of the body.
This range is crucial: An autoimmune disease doesn’t follow a fixed pattern. It can develop quietly, appear in very different places, and thus remain undetected for a long time.
Many Faces: An Overview of Over 60 Autoimmune Diseases
Experts estimate there are more than 60 different autoimmune diseases. Some are widespread, others are rarer, with many not immediately associated with the immune system in everyday life.
Type 1 Diabetes
Among the most well-known is Type 1 diabetes. Here, the immune system attacks the insulin-producing cells of the pancreas.
Hashimoto’s Thyroiditis and Graves’ Disease
Both affect the thyroid. While Hashimoto’s usually leads to hypothyroidism in the long term, Graves’ disease causes hyperthyroidism.
Multiple Sclerosis
In the nervous system, multiple sclerosis is one of the most well-known autoimmune diseases. It affects the brain and spinal cord and can cause very different symptoms depending on which areas are affected.
Crohn’s Disease and Celiac Disease
Both diseases affect the intestine. Crohn’s disease often occurs in episodes, while celiac disease triggers an inflammatory reaction to gluten.
Psoriasis and Alopecia Areata
Psoriasis manifests as inflammatory skin changes. In alopecia areata (circular hair loss), the immune reaction targets the hair follicles.
Lupus Erythematosus and Rheumatoid Arthritis
Lupus erythematosus is a particularly complex form. This autoimmune disease can be limited to the skin but also affect multiple organs simultaneously–including joints, kidneys, or the nervous system. Rheumatoid arthritis also falls into this category. It primarily affects the joints but can also involve other organs.
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Not Clearly Defined: Special Cases
Vitiligo holds a special position. It manifests as light skin patches. Whether it is definitively considered an autoimmune disease is not yet conclusively determined. However, it is associated with autoimmune processes and often occurs alongside other autoimmune diseases.
These examples show how varied an autoimmune disease can be and how many areas of the body can be affected.
How Common Are Autoimmune Diseases in Germany?
Autoimmune diseases are widespread in Germany. Their prevalence has significantly increased in recent years. In 2022, more than 6.3 million people with statutory health insurance were affected by at least one diagnosed autoimmune disease. This corresponds to about one in twelve insured individuals, or roughly 8.6 percent.6
Notable is the development over time: Between 2012 and 2022, the number of diagnosed cases increased–from about 7.1 percent to 8.6 percent. One reason for this is likely that autoimmune diseases are now recognized earlier and more accurately. The most common forms include diseases like Hashimoto’s thyroiditis, psoriasis, Type 1 diabetes, rheumatoid arthritis, and Crohn’s disease. A clear difference is also evident between genders. Women are significantly more affected than men. About 63.9 percent of new diagnoses are in women.
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Why Diagnosing the Disease Is Often a Puzzle
Recognizing an autoimmune disease is not easy. The reason: There are no typical symptoms that clearly indicate it. Depending on which organ is affected, the complaints look completely different. That’s why suspicion is often raised late, usually when other causes have been ruled out. When initial clues emerge, the actual diagnostics begin. Blood tests play a central role here. Doctors primarily look at two things:
- Inflammation markers that show whether the immune system is active.
- So-called autoantibodies–defense substances that target the body itself.
However, these values are not definitive proof. Not everyone with autoantibodies is sick. And not every autoimmune disease can be clearly detected through them. Therefore, a blood test alone is usually not enough.
Depending on the symptoms, further examinations are added. These include, for example, ultrasound examinations to look at organs more closely. In other cases, colonoscopies, tissue samples, or neurological tests are necessary. In the end, the diagnosis is often not a single result but a complete picture–assembled from many small clues.7
Treatment of an Autoimmune Disease
An autoimmune disease cannot currently be cured. This is mainly because the exact causes are not yet fully understood. Nevertheless, treatment is important. Untreated, the inflammations can permanently damage organs. The goal is therefore to alleviate symptoms and slow the progression of the disease.8
When the Body Needs Support
How exactly treatment is carried out depends greatly on the specific disease. Sometimes the body needs support because certain functions fail. For Type 1 diabetes, this means supplying insulin. For Hashimoto’s, it means replacing missing thyroid hormones.
Medications Against Inflammation and Misdirection
Additionally, there are medications that directly affect the immune system. Some inhibit inflammation, such as certain pain and anti-inflammatory medications or cortisone. Others go a step further and suppress the immune system overall. These so-called immunosuppressants can be effective–but also increase susceptibility to infections.9
Targeted Therapies: Modern but Not Risk-Free
There are also modern therapies that intervene more specifically. These include immunomodulating medications like biologics or beta-interferons. They aim to correct the misdirection of the immune system.
Supportive Measures in Everyday Life
Depending on the disease, additional supportive measures are used. Physical therapy can help with joint issues, light therapy with skin conditions like psoriasis. Everyday life also plays a role. Factors like stress, diet, or exercise can influence the course and are therefore increasingly considered. The treatment of an autoimmune disease is usually long-term–and always individually tailored.