COVID-19 and Autoimmunity: How the Virus Can Trigger New Diseases

Introduction: COVID-19 and the Immune System

The SARS-CoV-2 virus, which causes COVID-19, is known for its multifaceted impact on the human body. In addition to acute respiratory symptoms, it is capable of triggering complex immune reactions that in some cases lead to the development or exacerbation of autoimmune diseases [2, 3]. There is a growing body of evidence that COVID-19 can act as a trigger for various autoimmune conditions affecting both individual organs and entire body systems [3, 4].

The Thyroid Gland Under Attack: Autoimmune Thyroidopathies

One of the most frequently described autoimmune complications following a coronavirus infection is thyroid disease [3]. In particular, cases of newly diagnosed hyperthyroidism and Graves' disease, as well as exacerbations of pre-existing autoimmune thyroidopathies, have been reported [1, 2, 3].

• For example, a 28-year-old woman with no prior history of thyroid problems developed hyperthyroidism 8 weeks after contracting COVID-19, confirmed by low thyroid-stimulating hormone (TSH) levels, high free thyroxine (T4), and the presence of TSH receptor antibodies [1].
• A similar case was documented in a male teenager who was newly diagnosed with Graves' disease and psoriasis vulgaris following COVID-19 [4].
• The SARS-CoV-2 virus can affect the immune system and the thyroid gland directly, triggering pathological processes [1, 3].

Studies show an increased prevalence of autoimmune thyroid disease (AITD) in individuals who have had COVID-19 [6, 8]. A systematic review of 46 studies involving 3,856 patients confirms that COVID-19 can induce or worsen immune-mediated thyroid dysfunction [3]. Interestingly, patients with stable Hashimoto's thyroiditis sometimes developed Graves' disease after COVID-19, indicating a shift in the immune response [2].

Symptoms and Diagnosis of Autoimmune Diseases After COVID-19

Symptoms of autoimmune thyroid diseases can be diverse and depend on the type of disorder. In hyperthyroidism (e.g., in Graves' disease), patients may experience palpitations, nervousness, weight loss, hand tremors, excessive sweating, and sleep problems. In hypothyroidism (e.g., in Hashimoto's thyroiditis), fatigue, weight gain, dry skin, constipation, and depressive states are characteristic.

Given the potential link to COVID-19, when evaluating patients with "long COVID syndrome," it is extremely important to conduct a thorough examination, including an assessment of thyroid function [4]. Diagnosis includes laboratory blood tests to determine the levels of TSH, free T4, and T3, as well as specific antibodies:

• TSH receptor antibodies (TRAb) for Graves' disease [1];
• thyroperoxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) for Hashimoto's thyroiditis [6].

If elevated antibody levels are detected, an ultrasound of the thyroid gland may be recommended to assess its structure [6].

Other Autoimmune Manifestations and the Role of Vaccination

In addition to thyroid diseases, COVID-19 has also been linked to the development of other autoimmune conditions. For instance, the aforementioned teenager with Graves' disease also developed psoriasis vulgaris following the infection [4]. It is also worth noting that the SARS-CoV-2 virus and vaccines against it can affect the immune system. For example, cases of new-onset or exacerbated vitiligo following COVID-19 vaccination have been reported [7]. This highlights the complexity of the interaction between the virus and immunity.

It is important to note that, according to one study, the presence of pre-existing autoimmune diseases such as autoimmune gastritis, celiac disease, or type 1 diabetes in patients not taking immunosuppressive drugs did not increase their susceptibility to COVID-19 infection compared to the general population [5]. This suggests that the mechanisms underlying the development of new autoimmune conditions after COVID-19 may differ from the infection's impact on pre-existing diseases.

Treatment Approaches and Perspectives

Treatment approaches for autoimmune diseases that develop after COVID-19 generally follow standard protocols for these conditions. For example, in the case of hyperthyroidism caused by Graves' disease, antithyroid medications such as methimazole (thiamazole) are successfully used, and beta-blockers may be used to control symptoms [1]. Treatment for Hashimoto's thyroiditis with hypothyroidism involves levothyroxine hormone replacement therapy. Therapy for other autoimmune diseases, such as psoriasis or vitiligo, is also selected individually depending on the severity and extent of the process.

The importance of early diagnosis and timely initiation of treatment cannot be overstated, as this helps control symptoms, prevent complications, and improve patients' quality of life. Given the novelty of the problem, further large-scale studies are needed to fully understand the mechanisms underlying the development of autoimmunity after COVID-19 and to develop more targeted and effective treatments.

References

1. Thyroid disease post-COVID-19 infection: Report of a case with new-onset autoimmune thyroid disease. (Asia Pacific allergy, 2023). PubMed
2. Development of autoimmune thyroid disease after COVID-19 infection: case report. (Frontiers in medicine, 2024). PubMed
3. Autoimmune Thyroid Diseases After COVID-19 Infection: A Systematic Review of Clinical Manifestation and Outcomes. (International journal of environmental research and public health, 2026). PubMed
4. Autoimmune Thyroid Disease and Psoriasis Vulgaris after COVID-19 in a Male Teenager. (Case reports in pediatrics, 2021). PubMed
5. Impact of COVID-19 in immunosuppressive drug-naïve autoimmune disorders: Autoimmune gastritis, celiac disease, type 1 diabetes, and autoimmune thyroid disease. (Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology, 2022). PubMed
6. Increased prevalence of autoimmune thyroid disease after COVID-19: A single-center, prospective study. (Frontiers in endocrinology, 2023). PubMed
7. COVID-19 vaccine-associated vitiligo: A cross-sectional study in a tertiary referral center and systematic review. (The Journal of dermatology, 2023). PubMed
8. Association of COVID-19 with thyroid dysfunction and autoimmune thyroid disease: A retrospective cohort study. (Journal of translational autoimmunity, 2024). PubMed

The information provided in the article is for reference purposes only and cannot replace a consultation with a qualified medical specialist. Always consult a physician for diagnosis and treatment.