Sarcoidosis is an inflammatory disease. Questions have arisen about a potential connection between sarcoidosis and COVID-19. This article explores sarcoidosis and its relationship with COVID-19.
Understanding Sarcoidosis
Sarcoidosis is an inflammatory condition characterized by the formation of tiny collections of immune system cells, known as granulomas, in various organs of the body. These granulomas most commonly affect the lungs and lymph nodes in the chest, but can develop almost anywhere.
The symptoms of sarcoidosis vary widely depending on which organs are involved and the extent of the inflammation. General symptoms can include fatigue, fever, weight loss, and swollen lymph nodes. When the lungs are affected, individuals may experience a persistent dry cough or shortness of breath. Skin manifestations can appear as tender, red bumps, often on the shins, or rashes of small, itchy bumps.
The exact cause of sarcoidosis remains unknown. However, research suggests it involves an abnormal immune response to environmental triggers in genetically predisposed individuals.
The Role of Infections in Sarcoidosis
Scientists have long investigated the possibility that various infectious agents, including viruses, bacteria, and fungi, could trigger sarcoidosis. The hypothesis is that an infection might initiate or worsen the immune system’s response, leading to granuloma formation.
Some studies indicate a strong association between sarcoidosis and certain bacteria, such as mycobacteria and Propionibacterium acnes. While direct causal relationships are difficult to establish, the idea that an infection could act as a trigger for an aberrant immune response in genetically susceptible individuals is widely considered.
COVID-19 as a Potential Trigger
Emerging evidence and observational studies suggest a possible link between SARS-CoV-2 infection and the development or exacerbation of sarcoidosis. Case reports have documented new-onset sarcoidosis or sarcoidosis flares occurring after COVID-19 infection. Some patients have developed sarcoid-like granulomas as part of post-COVID-19 syndrome.
A systematic review found that new-onset sarcoidosis after COVID-19 infection predominantly affected the pulmonary system, but also presented with cutaneous, cardiac, and ocular manifestations. The mean time between COVID-19 infection and sarcoidosis diagnosis in these cases ranged from 10 to 140 days. These early findings indicate a possible association, particularly in patients experiencing severe COVID-19 or prolonged symptoms, often referred to as Long COVID.
How COVID-19 Might Initiate Sarcoidosis
The proposed biological mechanisms by which COVID-19 could trigger sarcoidosis involve significant immune system changes. One theory centers on immune dysregulation, such as the “cytokine storm” observed in severe COVID-19. This involves an uncontrolled release of pro-inflammatory cytokines, which are signaling molecules that can lead to widespread inflammation. Similar cytokine profiles are seen in both severe COVID-19 and sarcoidosis, suggesting a shared inflammatory pathway.
Another mechanism involves persistent viral antigens. Even after the acute infection resolves, fragments of the SARS-CoV-2 virus or its components might remain in the body, continuously stimulating the immune system. This prolonged presence could act as a persistent trigger, driving the immune response towards granuloma formation in genetically susceptible individuals. Additionally, the virus might unmask a pre-existing genetic predisposition to sarcoidosis. Studies have identified common gene expression patterns between COVID-19 and sarcoidosis, particularly those related to cytokine production and immune cell activation, further supporting a potential link.