What is the disease that causes nodules?

September 26, 2025 •

5 min read

According to the American Thoracic Society, sarcoidosis is a disease where inflammatory cells form tiny clumps called granulomas, or nodules, which can affect organs throughout the body, most notably the lungs. Knowing the potential causes of nodules, such as sarcoidosis, is a critical step toward understanding your health.

Quick Summary

Nodules are firm lumps of tissue caused by various conditions, including inflammatory disorders like sarcoidosis, autoimmune diseases such as rheumatoid arthritis and lupus, and infections like tuberculosis. While many are benign, it is important to seek a medical evaluation to determine the specific cause and rule out more serious issues.

Key Points

Sarcoidosis: An inflammatory disease where the immune system forms granulomas, or nodules, most commonly in the lungs, lymph nodes, and skin.
Autoimmune Causes: Conditions like rheumatoid arthritis (RA) can cause firm rheumatoid nodules under the skin, while a rare form of lupus can cause painful subcutaneous nodules.
Infectious Triggers: Bacterial and fungal infections, such as tuberculosis and histoplasmosis, are also known to cause nodule formation.
Diagnosis is Key: Distinguishing between the various causes requires a medical evaluation, which may include imaging (X-ray, CT) and possibly a biopsy to determine if the nodule is benign or malignant.
Treatment Varies: Management depends on the underlying cause, ranging from simple monitoring for benign nodules to medication (like corticosteroids) or surgery for more severe cases.
Consult a Doctor: Any new or changing nodule should be evaluated by a healthcare professional to ensure proper diagnosis and timely treatment.

What is a Nodule?

At its core, a nodule is a small, solid, and often firm growth of tissue. While some people may associate nodules solely with cancer, the vast majority are benign, or noncancerous. They can appear in or on any organ or tissue, from the lungs and thyroid gland to the skin and vocal cords. Nodules are essentially a cluster of cells, and their composition can vary greatly depending on the underlying cause. Some are formed from inflammatory cells, while others are a result of tissue overgrowth or the accumulation of other substances, such as urate crystals in gout. Understanding their formation is key to differentiating between the many conditions that cause them.

Sarcoidosis: A Primary Cause of Nodules

Sarcoidosis is a rare inflammatory disease characterized by the formation of granulomas, which are small, inflammatory nodules. The exact cause is unknown, but it is believed to be an abnormal immune system response triggered by environmental factors in genetically susceptible individuals.

Where Sarcoidosis Nodules Appear

Lungs: This is the most common location, with granulomas leading to symptoms such as a persistent cough, shortness of breath, or chest pain. In severe cases, this can result in permanent lung scarring, known as pulmonary fibrosis.
Skin: Skin nodules are a classic sign of sarcoidosis. These can manifest as tender, reddish-purple bumps on the shins (erythema nodosum) or raised, reddish-purple patches on the nose and cheeks (lupus pernio).
Lymph Nodes: Swollen lymph nodes are a frequent occurrence, often in the chest, neck, armpit, or groin.
Eyes: Nodules in the eye can cause inflammation (uveitis), leading to redness, pain, or blurred vision.

Autoimmune Diseases and Their Associated Nodules

Several autoimmune conditions can cause nodules, which are often a key diagnostic indicator.

Rheumatoid Arthritis (RA)

Approximately 25% to 40% of people with moderate to severe RA will develop rheumatoid nodules.

Characteristics: These are firm, non-painful, subcutaneous bumps that form under the skin.
Locations: They are most common on the extensor surfaces of joints, such as the elbows, fingers, and knuckles. They can also develop in other areas of the body, including the lungs, heart, and vocal cords, though this is rare.

Lupus Erythematosus

Lupus is another autoimmune disease that can lead to nodule formation, particularly in a rare subtype known as lupus erythematosus panniculitis (LEP) or lupus profundus.

Characteristics: LEP causes painful, inflamed lumps under the skin, often in the fat layer.
Consequences: These nodules can lead to scarring and depressions in the skin (lipoatrophy) as they heal.

Infectious and Neoplastic Causes

Nodules can also be the body's response to infection or, in some cases, a sign of malignancy.

Infectious Nodules

Fungal Infections: Diseases like histoplasmosis and coccidioidomycosis can cause lung nodules, which are often granulomas formed by immune cells.
Bacterial Infections: Tuberculosis is a classic example of an infection that can cause granulomatous nodules, especially in the lungs and lymph nodes.

Malignancy

While less common, cancerous growths can present as nodules.

Cancer: Malignant nodules can form in organs like the lungs or thyroid gland. It is crucial to determine if a nodule is benign or malignant, which often requires a biopsy.
Lymphoma: Enlarged lymph nodes containing nodules can sometimes be a sign of lymphoma or leukemia.

Distinguishing Nodular Diseases: A Comparison Table

To help illustrate the differences between common nodule-forming diseases, the following table provides a comparison of their key features.


Feature	Sarcoidosis	Rheumatoid Arthritis	Lupus Panniculitis	Infections (e.g., Fungal)
Cause	Unknown; believed to be immune response to trigger	Autoimmune attack on joint tissue	Autoimmune attack on skin's fat layer	Immune response to microorganisms
Common Locations	Lungs, lymph nodes, skin, eyes	Extensor surfaces (elbows, fingers), lungs (rare)	Subcutaneous fat (arms, shoulders, face)	Lungs, lymph nodes
Appearance	Reddish-purple bumps, patches	Firm, rubbery, or hard bumps under skin	Painful, inflamed, deeper lumps	Granulomas often seen on imaging
Symptoms	Cough, shortness of breath, fatigue, eye pain	Joint pain, stiffness, systemic inflammation	Tenderness, skin lesions, potential scarring	Cough, fever, and symptoms specific to infection
Prognosis	Variable; often resolves spontaneously; can be chronic	Variable; nodules may indicate more severe disease	Treatable, but can recur; may cause scarring	Depends on type of infection and treatment effectiveness

Diagnosis and Management

Proper diagnosis of a nodule's underlying cause is essential for effective treatment. A doctor will typically begin with a physical examination and take a full medical history.

Diagnostic Steps

Imaging Tests: X-rays, CT scans, or ultrasounds are used to visualize and characterize the nodule's size, shape, and location.
Blood Tests: These can check for inflammatory markers, antibodies (like rheumatoid factor), or indicators of infection.
Biopsy: For nodules with suspicious characteristics, a biopsy—the removal of a small tissue sample for lab analysis—is often necessary to rule out malignancy.

Treatment Approaches

Treatment is directed at the underlying cause. For benign conditions like mild sarcoidosis or RA, monitoring may be sufficient. Other cases may require medication.

Corticosteroids and Immunosuppressants: These are commonly used to reduce inflammation in conditions like sarcoidosis and rheumatoid arthritis.
Anti-malarial drugs: Can be effective for some cutaneous lupus conditions.
Surgery: May be necessary to remove large nodules that cause symptoms or prove to be malignant.

What to Do If You Discover a Nodule

It is always advisable to consult a healthcare provider if you discover a nodule or new bump on your body, especially if it changes in size or is accompanied by other symptoms. While many nodules are harmless, it is important to get a professional medical opinion for an accurate diagnosis and treatment plan.

For more in-depth information on sarcoidosis, a key disease that causes nodules, visit the American Lung Association website.

Conclusion

While a single disease does not cause all nodules, sarcoidosis is a prominent inflammatory condition known for creating granulomas, or nodules, in various body parts. Other autoimmune diseases like rheumatoid arthritis and lupus, along with infections and malignancies, are also potential culprits. Correctly identifying the cause is a multi-step process involving physical exams, imaging, and sometimes a biopsy. Ultimately, understanding the origin of a nodule is the first step toward effective management and peace of mind.

Frequently Asked Questions

No, most nodules are benign, or noncancerous. They can result from a variety of causes, including infections, inflammation, or autoimmune conditions. A doctor can determine the nature of a nodule through examination and further testing.

While cancer is a concern, the most common cause of benign lung nodules is infectious granulomas, which are clumps of immune cells that form in response to fungal or bacterial infections. Noninfectious inflammatory conditions like sarcoidosis also frequently cause lung nodules.

Doctors diagnose nodules through a combination of a physical exam, taking a medical history, and ordering imaging tests like X-rays, CT scans, or ultrasounds. In cases where malignancy is suspected, a biopsy is performed to analyze a tissue sample.

Yes, rheumatoid arthritis can cause rheumatoid nodules, which are firm, non-tender bumps that typically form under the skin near joints. They can also occur in internal organs in rare cases.

Sarcoidosis nodules can vary in presentation. While some skin manifestations, such as erythema nodosum, are tender and painful, other nodules may be painless. The symptoms depend heavily on their location and size.

Yes, a rare form of lupus called lupus panniculitis (or lupus profundus) can cause painful, inflamed lumps or nodules in the fat layer beneath the skin. These can sometimes leave scars or depressions after healing.

It depends on the cause. For some conditions like mild sarcoidosis or certain rheumatoid nodules, they may resolve on their own. Others, especially those caused by chronic conditions or malignancy, may require medical treatment.