Autoimmune diseases are a group of pathologies of unknown cause, but with a genetic predisposition. They are characterized because they usually produce an immune disorder in which the body’s defenses are turned against itself, normally with the production of autoantibodies and inflammatory states that can alter one or several organs.
They affect approximately 15% of the population and usually have a chronic course, most frequently affecting women of childbearing age, and usually cause a poor quality of life for sufferers, as well as a significant consumption of drugs to avoid the multiple symptoms.
Currently, about 80 autoimmune diseases are known, and in another 40 non-autoimmune diseases there is evidence of an underlying immunological alteration. Depending on whether the immune reaction attacks one or several tissues, autoimmune diseases can be classified into two groups.
Classification of autoimmune diseases
- Organ-specific autoimmune diseases are those produced by antibodies that attack a specific organ or tissue. The best known can be grouped according to the tissue affected:
- Autoimmune diseases of the nervous system: myasthenia gravis and multiple sclerosis;
- Autoimmune diseases of the blood: idiopathic thrombocytopenic purpura and autoimmune hemolytic anemia;
- Autoimmune diseases of the liver: primary biliary cirrhosis and autoimmune hepatitis;
- Autoimmune diseases of the pancreas: type 1 diabetes and autoimmune pancreatitis;
- Autoimmune diseases of the gastric mucosa: atrophic gastritis-vitamin B12 deficiency;
- Autoimmune diseases of the intestine: Crohn’s disease, ulcerative colitis and celiac disease;
- Autoimmune diseases of the thyroid: Hashimoto’s thyroiditis-hypothyroidism and Graves’ hyperthyroidism;
- Autoimmune diseases of the adrenal capsules: adrenal insufficiency-Addison’s disease;
- Other autoimmune diseases: autoimmune pituitary, uveitis, vitiligo, pemphigus, psoriasis, etc.
- Systemic autoimmune diseases: are those in which immune reactions cause lesions in various organs. The main systemic autoimmune diseases are rheumatoid arthritis, lupus erythematosus, antiphospholipid syndrome, Sjögren’s syndrome, scleroderma, mixed connective tissue disease, dermatomyositis, indeterminate connective tissue disease, ANCA-associated vasculitis and Goodpasture’s syndrome.
Genetic factor in autoimmune diseases
Although the cause of autoimmune diseases is not known, it is known that there is a genetic predisposition and that they are more frequent in women.
It is also believed that certain environmental triggers may be necessary for them to appear, such as the action of germs and toxins, drugs or contamination in food. It is also important to highlight the importance of stress, both in the appearance of autoimmune disease and in the production of symptom outbreaks. On the other hand, also the microbiome is being considered a factor in the development of autoimmune pathology, more specifically the gut microbiota.
Symptoms and complications of autoimmune diseases
The symptoms of localized autoimmune diseases vary depending on the organ affected, and will be related to organ failure or inflammation.
As for systemic autoimmune diseases, there can be a wide variety of non-specific symptoms, such as fever, fatigue, loss of appetite and weight loss; and other more specific symptoms such as skin, osteoarticular, hematologic involvement, and symptoms derived from the involvement of vital organs such as the heart, nervous system, lungs or kidneys.
Complications can also arise, in addition to the disease itself, due to immunosuppressive treatments, such as increased cardiovascular risk, increased incidence of osteoporosis, cancer and infections. Finally, patients with an autoimmune disease are more likely to contract another autoimmune disease, known as overlap syndromes.
Why autoimmune diseases are difficult to detect
As autoimmune diseases usually affect many organs and present a wide variety of symptoms, patients often consult numerous specialists before a diagnosis is established.
The specific diagnosis is made on the basis of the clinical history and physical examination, with the help of complementary tests such as the determination of autoantibodies. Among these, the most sensitive and least specific are the antinuclear antibodies, which are present in most autoimmune diseases. On the other hand, some of the most specific or characteristic antibodies are anti native DNA and anti Sm in systemic lupus erythematosus, anti cyclic citrullinated peptide in rheumatoid arthritis, anti SSA/Ro and anti SSB/La in Sjögren’s syndrome.
Thus, anemia, decreased leukocyte and platelet counts, and elevated inflammatory parameters such as C-reactive protein, fibrinogen and erythrocyte sedimentation rate can be detected in the basic general laboratory workup. The presence of alterations in the urinalysis, such as proteinuria, hematuria or cylindruria, or in renal function, support the diagnosis of renal complication.
In some cases the study should be completed with diagnostic tests of joints, thorax, heart, etc., such as electromyography, isotopic studies and biopsies.
Advances in the treatment of autoimmune diseases
Localized autoimmune diseases are treated with hormone replacement in endocrinological organ-specific diseases and gluten withdrawal in celiac disease.
In systemic diseases, or organospoechoic diseases affecting vital organs, the mainstays of treatment are anti-inflammatory drugs, antimalarials, corticosteroids and immunosuppressants, as well as modern biological therapies, which have undergone spectacular development in recent years. These will be indicated according to the type of disease, the organs affected and the body’s response to less aggressive therapies.
Lately, hematopoietic cell transplantation has become more important, with increasingly better results being obtained in patients who have not responded favorably to conventional and biological therapies.
With the progress in research and knowledge of these diseases, it is foreseeable that significant progress will be made in the coming years in their management and treatment, and even the possible development of vaccines.