An autoimmune disease is a condition that results from an anomalous response of the adaptive immune system, wherein it mistakenly targets and attacks healthy, functioning parts of the body as if they were foreign organisms.

Symptoms are often diverse and can be fleeting, fluctuating from mild to severe, and typically comprise low-grade fever, fatigue, and general malaise.

[7] While some diseases like lupus exhibit familial aggregation, suggesting a genetic predisposition, other cases have been associated with infectious triggers or exposure to environmental factors, implying a complex interplay between genes and environment in their etiology.

[1] Therapeutic approaches primarily aim to manage symptoms, reduce immune system activity, and maintain the body's ability to fight diseases.

[1] The initial recognition of autoimmune diseases dates back to the early 1900s, and since then, advancements in understanding and management of these conditions have been substantial, though much more is needed to fully unravel their complex etiology and pathophysiology.

[1] These shared symptoms occur as a result of the body's immune system mistakenly attacking its own cells and tissues, causing inflammation and damage.

On the other hand, type 1 diabetes, which results from an autoimmune attack on the insulin-producing cells of the pancreas, primarily presents with symptoms related to high blood sugar, such as increased thirst, frequent urination, and unexplained weight loss.

[14] The appearance of these signs and symptoms can not only provide clues for the diagnosis of an autoimmune condition, often in conjunction with tests for specific biological markers, but also help monitor disease progression and response to treatment.

[15] Ultimately, due to the diverse nature of autoimmune diseases, a multidimensional approach is often needed for the management of these conditions, taking into consideration the variety of symptoms and their impacts on individuals' lives.

The binding of the autoantibodies to the receptors results in unregulated production and release of thyroid hormone,[23] which can lead to stimulatory effects such as rapid heart rate, weight loss, nervousness, and irritability.

[31] Type 1 diabetes is a condition resulting from the immune system attacking insulin-producing beta cells in the pancreas, leading to high blood sugar levels.

The exact causes of autoimmune diseases remain largely unknown;[7] however, research has suggested that a combination of genetic, environmental, and hormonal factors, as well as certain infections, may contribute to the development of these disorders.

[1] The human immune system is equipped with several mechanisms to maintain a delicate balance between defending against foreign invaders and protecting its own cells.

[34] Experimental methods like genome-wide association studies have proven instrumental in pinpointing genetic risk variants potentially responsible for autoimmune diseases.

[36][37] There is increasing evidence that certain genes selected during evolution offer a balance between susceptibility to infection and the capacity to avoid autoimmune diseases.

[38] Several experimental methods such as the genome-wide association studies have been used to identify genetic risk variants that may be responsible[39] for diseases such as type 1 diabetes and rheumatoid arthritis.

Current research suggests that up to seventy percent of autoimmune diseases could be attributed to environmental influences, which encompass an array of elements such as chemicals, infectious agents, dietary habits, and gut dysbiosis.

However, a unifying theory that definitively explains the onset of autoimmune diseases remains elusive, emphasizing the complexity and multifaceted nature of these conditions.

[46] Furthermore, analysis of large-scale data has revealed a significant link between SARS-CoV-2 infection (the causative agent of COVID-19) and an increased risk of developing a wide range of new-onset autoimmune diseases.

[57] For instance, research suggests that the bacterium that causes strep throat, Streptococcus pyogenes, might trigger rheumatic fever, an autoimmune response affecting the heart.

If these protective mechanisms fail, a pool of self-reactive cells can become functional within the immune system, contributing to the development of autoimmune diseases.

This phenomenon, known as molecular mimicry, can lead to cross-reactivity, where the immune response to such infections inadvertently results in the production of antibodies that also react with self-antigens.

[63] An example of this is Guillain–Barré syndrome, in which antibodies generated in response to a C. jejuni infection also react with the gangliosides in the myelin sheath of peripheral nerve axons.

Generally, the diagnostic process involves a combination of medical history evaluation, physical examination, laboratory tests, and, in some cases, imaging or biopsies.

[65] The first step in diagnosing autoimmune disorders typically involves a thorough evaluation of the patient's medical history and a comprehensive physical examination.

For example, chest x-rays or CT scans can identify lung involvement in diseases like rheumatoid arthritis or systemic lupus erythematosus, while an MRI can reveal inflammation or damage in the brain and spinal cord in multiple sclerosis.

[11] Standard treatment methods include:[11] Traditional treatment options include immunosuppressant drugs to reduce the immune response against the body's own tissues, such as:[68] Because immunosuppressants weaken the overall immune response, relief of symptoms must be balanced with preserving the patient's ability to combat infections, which could potentially be life-threatening.

[76] In both autoimmune and inflammatory diseases, the condition arises through aberrant reactions of the human adaptive or innate immune systems.

[84] According to the hygiene hypothesis, high levels of cleanliness expose children to fewer antigens than in the past, causing their immune systems to become overactive and more likely to misidentify own tissues as foreign, resulting in autoimmune or allergic conditions such as asthma.

[86][87] A deficiency in vitamin D, from hereditary or environmental influence, can lead to a more inefficient and weaker immune response and seen as a contributing factor to the development of autoimmune diseases.