Sarcoidosis is an inflammatory disease defined by the formation of granulomas, which are tiny clusters of immune cells. These granulomas can appear in any organ but most commonly develop in the lungs and lymph nodes. When too many granulomas accumulate in an organ, they can interfere with its normal function.
What Causes Sarcoidosis
The precise cause of sarcoidosis remains unknown. The prevailing theory suggests the condition arises from an overactive immune response to specific triggers in individuals who are genetically predisposed. This means a person’s genetic makeup may make them more susceptible when exposed to certain substances. The condition is not considered an autoimmune disorder, despite the immune system’s involvement.
Potential triggers are thought to include environmental or infectious agents like bacteria, viruses, dust, and chemicals. For instance, exposure to insecticides or working near wood stoves has been considered as possible factors. A study known as the ACCESS trial did not identify a single unifying trigger, suggesting the cause is a complex interaction between multiple genetic and environmental components. The condition can also run in families, indicating that family history is a risk factor.
Symptoms and Affected Organs
The signs of sarcoidosis are highly variable and depend on which organs are affected. For some, the disease begins with a sudden onset of symptoms, while for others, it develops gradually over many years. General, non-specific symptoms often include fatigue that is not relieved by sleep, fever, unexplained weight loss, and swollen lymph nodes, particularly in the neck, armpits, or groin. Joint pain and swelling, especially around the ankles, can also be an early indicator.
Since sarcoidosis affects the lungs in approximately 90% of cases, respiratory issues are very common. Patients with pulmonary sarcoidosis frequently experience a persistent dry cough, shortness of breath, and chest pain or discomfort. In some instances, individuals may also produce a wheezing sound when breathing.
The skin is the second most commonly affected organ. Skin-related symptoms can include a rash of small, itchy bumps or growths under the skin, especially around existing scars or tattoos. A characteristic sign is erythema nodosum, which presents as red, tender bumps on the shins. Another distinct skin lesion is lupus pernio, which causes raised, purplish sores on the nose, cheeks, lips, and ears.
Eye involvement, or ocular sarcoidosis, can lead to serious vision problems if not addressed. Symptoms often include blurred vision, eye pain, significant redness, and a heightened sensitivity to light. This is due to inflammation in different parts of the eye, such as uveitis. While less common, sarcoidosis can impact the heart, causing irregular heartbeats or fainting, and the nervous system, leading to headaches or facial palsy.
The Diagnostic Process
Diagnosing sarcoidosis can be a complex process because its symptoms often mimic those of other illnesses. Physicians arrive at a diagnosis by first ruling out other potential conditions. The process begins with a review of a patient’s medical history and a complete physical examination to check for swollen lymph nodes and examine any skin lesions.
Imaging tests are a fundamental part of the diagnostic workup. A chest X-ray is one of the most common initial tests used to look for inflammation and swollen lymph nodes (hilar lymphadenopathy). For a more detailed view, a high-resolution computerized tomography (CT) scan may be ordered. Other imaging techniques, such as PET scans or an MRI, might be used if there is suspicion of heart or nervous system involvement.
Blood and urine tests are performed to assess a patient’s overall health and how well organs like the liver and kidneys are functioning. These lab tests can help exclude other diseases and may reveal markers associated with sarcoidosis, such as elevated levels of calcium or angiotensin-converting enzyme. However, since these markers can be elevated in other conditions, they are not used for a definitive diagnosis on their own.
The most definitive method for confirming sarcoidosis is a biopsy. This procedure involves taking a small tissue sample from an affected organ, such as the skin, a lymph node, or the lungs. The sample is then examined under a microscope to look for the characteristic noncaseating granulomas, which helps confirm the diagnosis and differentiates it from other diseases.
Treatment and Management Approaches
Treatment for sarcoidosis is not always necessary, as the condition can resolve on its own. For patients with mild symptoms that do not threaten organ function, a “watchful waiting” approach of regular monitoring is often adopted.
When treatment is required, the first-line therapy is corticosteroids, such as prednisone. These anti-inflammatory medications reduce inflammation and prevent organ damage by suppressing the immune system. Treatment begins with a higher dose that is gradually tapered over several months.
For patients whose disease does not respond to corticosteroids or who cannot tolerate their side effects, other medications are considered. Immunosuppressants like methotrexate are common second-line treatments. In more severe cases, biologic medications known as TNF-alpha inhibitors, such as infliximab, may be prescribed when other treatments have failed.
Prognosis and Long-Term Outlook
The long-term outlook for individuals with sarcoidosis is generally positive. More than half of patients experience remission within two to five years, often without needing any treatment. In these cases, the granulomas disappear, and the disease is unlikely to return. The presence of certain initial symptoms, such as the skin rash erythema nodosum, can indicate a better prognosis.
A portion of individuals will develop chronic sarcoidosis, where the disease persists for many years and may require ongoing management. About 10% to 20% of those with chronic sarcoidosis may experience permanent organ damage, most commonly scarring in the lungs, known as pulmonary fibrosis. The overall mortality rate for the disease is low, at around 5%.