Your immune system protects you by defending the body from disease and infection. When your immune system detects a threat (such as a toxin, bacteria, or virus), it mounts an immune response and produces antibodies and white blood cells to fight the invader.

When you have an autoimmune disease, however, your immune system activates in an inappropriate or abnormal manner. Unable to distinguish between self and non-self proteins, a dysfunctional immune system mistakes the body’s own cells for harmful invaders. It produces cells and antibodies that target, attack, and damage healthy cells, tissues, and organs. This results in a wide spectrum of possible symptoms and severity.

There are 80-100 known autoimmune diseases, and many more conditions are autoimmune-related or include suspected autoimmune components. Many autoimmune diseases overlap, or exhibit comorbidities and coexisting symptoms. If you have three or more autoimmune diseases, this is known as Multiple Autoimmune Syndrome (MAS).

Some autoimmune diseases are organ-specific as they affect certain areas of the body, such as the joints, gastrointestinal tract, skin, or as in type 1 diabetes, the insulin-producing cells of the pancreas. Others are systemic, meaning that immune attack occurs in different tissues of the body. Examples of systemic autoimmune diseases are Sjögren’s syndrome, systemic lupus erythematosus, scleroderma, and rheumatoid arthritis.

There are over 80 autoimmune diseases (ADs) and counting, including many rare and also more common conditions. The consensus on which ADs are most common varies. It is likely based on patient-reported information, physician experience in-clinic, hospital data, and research studies. Based on current information, some of the most common autoimmune diseases include:

• Alopecia areata
• Celiac disease 
• Crohn’s disease (CD)
• Grave’s disease
• Hashimoto’s thyroiditis
• Multiple sclerosis (MS)
• Psoriasis
• Psoriatic arthritis (PA)
• Raynaud’s syndrome
• Rheumatoid arthritis (RA)
• Sjögren’s syndrome
• Systemic lupus erythematosus (SLE)
• Type I diabetes (T1D)
• Ulcerative colitis (UC)
• Vitiligo

Examples of common autoimmune-related or suspected conditions:

• Chagas disease
• Chronic fatigue syndrome (ME/CFS)
• Chronic urticaria (CU)
• Eczema
• Endometriosis
• Fibromyalgia
• Interstitial cystitis
• Lyme disease
• Postural orthostatic tachycardia syndrome (POTS)
• Restless leg syndrome (RLS)

There are also many rare autoimmune diseases. In the United States, a rare disease means that it affects fewer than 200,000 people. In many cases, there exists such little information that the true prevalence is unknown. To learn about rare diseases, head to the National Organization for Rare Disorders.

Certain risk factors are believed to impact immune tolerance and may lead to the development of autoimmune disease (AD):

• Your Sex – Hormonal differences and the presence of a second X chromosome are factors that may explain why up to 80% of people living with autoimmune disease are female. Males with an extra X chromosome are also more likely to develop AD.
• Genetics – Certain inherited genetic variations, such as the HLA Q8 and HLA Q2 genes, may impact immune response and predispose you to the development of autoimmune disease. As environmental factors can activate or deactivate genes, not everyone who is predisposed to AD will develop an illness.
• Having an autoimmune disease – The reason for this may involve genetic predisposition and environmental factors. Accumulation of three or more autoimmune conditions is called Multiple Autoimmune Syndrome (MAS), which is seen in roughly 25% of people with AD.
• Obesity – An increased amount of adipose (or fat) tissue sends the body into a chronic state of low-grade inflammation and can significantly alter immune system function. Metabolic syndrome and insulin resistance are also strongly associated with obesity.
• Smoking and exposure to toxic agents – The inhalation of toxic chemicals in cigarettes and exposure to air pollutants, organic solvents, and other toxins are associated with the development of autoimmune diseases.
• Medications – Blood pressure medications, cancer immunotherapy, antibiotics, and other pharmaceutical therapies may induce side effects that impact immune system function and leading to autoimmune disease.
• Infections – Infectious microorganisms, such as Epstein Barr Virus (EBV), SARS-CoV-2, and Group A Streptococcus, can turn on certain genes and impact the immune system’s ability to differentiate between self and non-self, thus triggering an autoimmune reaction. Various other viruses and bacteria are associated with development of AD, but their significance is not yet understood.

To learn more, check out: 7 Risk Factors for Autoimmune Disease

Rheumatologists are trained to diagnose and treat autoimmune and inflammatory diseases that affect the musculoskeletal system, as well as systemic conditions.

Other doctors who diagnose and treat autoimmune disease and related conditions:

• Dermatologists
• Endocrinologists
• Gastroenterologists
• Immunologists
• Internists
• Neurologists
• Functional medicine doctors
• Integrative medicine doctors
• Naturopathic doctors
• Osteopaths

You may choose to work with a combination of modern Western physicians and holistic practitioners to build your network of healthcare providers. It can be helpful to work with more than one expert in order to benefit from their additional knowledge, experience, and methods. They may offer fresh perspectives and be willing to communicate with each other, as the need arises, and coordinate your care.

In your doctor’s initial assessment, they will take your history, examine you, discuss your symptoms and risk factors, and order initial tests to search for clues. If they find an indication of what may be wrong, they can follow that lead through further diagnostic testing and analysis.

Testing is used in conjunction with your experiences and your doctor’s medical knowledge to investigate the underlying causes of your illness. Identifying complex, chronic conditions requires serious and compassionate detective work. The paths your doctor explores will depend on your particular symptoms, history, environment, and other details.

Listed below are a few examples of factors clinicians may look at and tests they may run to find answers. Understanding what tests are out there can help you get an idea of what may be involved in diagnosis and ask further questions.

Common autoimmune disease testing:

• Antinuclear antibodies (ANA) – high amounts or certain patterns of autoantibodies; often the first test used when autoimmune disease is suspected
• Autoantibodies – high levels of specific autoantibodies such as rheumatoid factor (RF), thyroid antibodies (TPO, TgAB, TSI), or antitransglutaminase antibodies can indicate conditions like rheumatoid arthritis, autoimmune thyroid conditions, and celiac disease
• Secretory IgA antibodies – selective IgA deficiency may occur in autoimmune diseases like rheumatoid arthritis, lupus, celiac disease, ulcerative colitis, and Crohn’s disease
• Thyroid function – complete panel may include TSH (or sensitive TSH), total T4, free T4, free T3, and reverse T3; can be used in diagnosing and monitoring Hashimoto’s thyroiditis, Grave’s disease, and other thyroid conditions
• Inflammation – C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) tests detect inflammatory markers
• Organ function – endoscopies, colonoscopies, x-rays, ultrasounds, and other tests check for damage to the liver, kidneys, large intestine, thyroid, and other organs and tissues that may be indicative of certain diseases

Other tests to understand the full picture of health and detect autoimmune or other conditions:

• Complete blood count (CBC)
• Comprehensive metabolic panel (CMP)
• Nutritional anemia profile
• Micronutrient deficiencies
• Glucose regulation and metabolism
• Organic acids test (OAT)
• Hormone levels
• Genetic testing
• Comprehensive stool analysis

Note: Some of the listed tests are more routinely ordered by functional medicine, integrative medicine, or naturopathic doctors.