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Diagnosing Sarcoidosis

Sarcoidosis is a condition that causes inflammation. It can occur in multiple organs, but it most often involves the lungs, skin, and lymph nodes. Doctors don’t know exactly what causes the condition, but they believe it may arise from the immune system’s response to environmental triggers. Specialists at NYU Langone’s Sarcoidosis Program use advanced tests to diagnose sarcoidosis anywhere it occurs in the body.

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Normally, the immune system responds to harmful substances or stimuli by releasing special cells to protect your body. These cells cause inflammation, but once the harmful substance is gone, the inflammation diminishes. In people with sarcoidosis, however, the inflammation does not subside, and inflammatory cells called granulocytes clump together. These clumps, or granulomas, appear in various organs, affecting their structure and, occasionally, their function.

In most people, sarcoidosis is acute, or sudden, and resolves on its own in a few weeks without treatment. In some instances, however, sarcoidosis becomes progressive and causes serious complications. Rarely, people with the condition have subtle symptoms that worsen over the course of weeks or months. This is considered chronic sarcoidosis and may require long-term, extensive medical therapy.

Symptoms and Risk Factors

Sarcoidosis is what’s known as a multisystem disorder. Symptoms vary depending on the affected body parts. It usually affects the lungs, so you may experience a cough, fever, and shortness of breath. If the lymph nodes are involved, they typically become enlarged.

Sarcoidosis may affect the skin, causing discolored, large bumps anywhere on the body. It may also affect the eyes, causing blurry vision or light sensitivity and can cause arthritis, fever, joint pain, and fatigue.

Rarely, the condition can affect the heart and cause an irregular heartbeat and shortness of breath, as well as cause serious complications such as heart failure. In a minority of patients, sarcoidosis can affect the nervous system—brain, spinal cord, nerves, or muscles. This is called neurosarcoidosis. Sometimes several organs are affected at the same time, which can make treating sarcoidosis a challenge.

Sarcoidosis tends to affect people between the ages of 20 and 60. Certain groups are at higher risk than others. In the United States, Black people have a higher incidence than other groups. Those with a family history of sarcoidosis also have an elevated risk.

Diagnostic Tests

To diagnose sarcoidosis, doctors take a medical history and conduct a thorough physical exam. They look for signs of sarcoidosis on the skin, eyes, and lymph nodes. They may also order several different tests, including blood, biopsies, and imaging tests.

Blood Tests

Your doctor may take a sample of your blood and test it for markers of inflammation. Inflammatory markers can be helpful in diagnosing the condition, especially if sarcoidosis is affecting organs other than your lungs. Your doctor may also test your blood for evidence of conditions that mimic sarcoidosis, such as tuberculosis.

Chest X-Ray

If you have a cough or shortness of breath, your doctor may order a chest X-ray, a fast, painless test that uses beams of energy to create an image of your chest, including your heart and lungs. A chest X-ray is an excellent initial diagnostic test that may reveal scar tissue, lung consolidation—a condition in which airways in the lungs partially fill with mucus or fluid—or enlarged lymph nodes.

CT Scan

Occasionally, a more detailed look is needed after a chest X-ray. A CT scan uses a computerized X-ray system to create 3D cross-sectional images of the body which provide more detail than X-rays.

To diagnose sarcoidosis, CT imaging is often used to examine small structures of the lungs to determine if granulomas may be present. A CT scan may also show evidence of lung scarring, and affected lymph nodes can be seen more clearly. Less commonly, CT imaging may be used to evaluate other areas of the body affected by sarcoidosis, such as the head and abdomen.


An ultrasound of the heart, called an echocardiogram, can look at the functioning of the heart to see if there are any signs of weakening of the walls of the heart. This can even occur in people without symptoms and may be a sign of sarcoidosis affecting the heart.

Cardiac MRI

This specialized MRI represents another way to look at the function of the heart, which can be difficult on standard MRI and CT scans. Cardiac MRIs can also help doctors diagnose swelling in the heart and scarring that can occur due to sarcoidosis.

PET/CT Scans

PET/CT scans combine the standard CT scan with a radiolabeled, or marked, sugar infusion. On the images produced, the concentration of radiolabeled glucose shows up as bright spots in areas of the body that are using lots of sugar in their metabolism. This often correlates with areas of inflammation from sarcoidosis.


An advanced imaging study combining PET and MRI technologies can be used to help differentiate active inflammation from areas of old or inactive disease, since the appearance can sometimes be similar. When it is necessary, this exam can provide an evaluation of the lungs, lymph nodes, the heart, and other organs typically affected by sarcoidosis.

Pulmonary Function Test

People with sarcoidosis may have trouble exhaling a normal amount of air. Pulmonary function testing assesses lung function and possible damage by measuring how much air your lungs can hold, how quickly you can inhale and exhale, and how much oxygen your lungs deliver to the blood.

Spirometry is the test most commonly used to measure pulmonary function. It measures how much and how quickly you can move air out of your lungs. During this test, you breathe into a mouthpiece attached to a recording device called a spirometer. The results may be printed out on a chart for your doctor to analyze.

Bronchoscopy with Biopsy

If sarcoidosis appears to affect your lungs, your doctor may perform a bronchoscopy, a test that enables the close examination of these organs. Your doctor inserts a bronchoscope, a thin, flexible tube with a light and a camera on the end, through your nose or mouth. With the help of a video monitor, they guide the instrument through the airways.

The doctor uses tiny instruments threaded through the bronchoscope to remove lung tissue samples, which are sent to a lab. A pathologist—a doctor who studies diseases in the laboratory—can help rule out or confirm a diagnosis of sarcoidosis.

Skin Biopsy

When sarcoidosis affects the skin, rashes and other symptoms can look similar to other dermatological conditions. Our dermatologists, part of NYU Grossman School of Medicine’s Ronald O. Perelman Department of Dermatology, have extensive experience in diagnosing sarcoidosis through clinical evaluation and skin biopsy, which can often spare biopsies of other organs.

During a skin biopsy, a dermatologist removes a very small piece of skin, a few millimeters wide, to send to a pathologist for diagnosis.

Lumbar Puncture

In patients with suspected neurosarcoidosis, a type of sarcoidosis that affects the nervous system, a lumbar puncture is sometimes necessary to assess for evidence of inflammation in the central nervous system. This is an outpatient procedure that is usually done under the guidance of real-time X-ray images.

The cerebrospinal fluid that circulates around the brain and spinal cord is analyzed for inflammatory cells and markers, such as cytokines and immunoglobulins that may be elevated in neurosarcoidosis.

A lumbar puncture is also helpful to exclude other conditions that may look similar to neurosarcoidosis. It is important that a lumbar puncture is ordered by a doctor experienced with neurosarcoidosis so that the cerebrospinal fluid is properly tested.