Can Sarcoidosis Be Misdiagnosed as Lupus?

Understanding Sarcoidosis and Lupus: Two Distinct Conditions

Sarcoidosis is a systemic inflammatory disease characterized by the formation of granulomas—tiny clumps of inflammatory cells—in various organs. It most commonly affects the lungs and lymph nodes, where imaging often reveals distinct nodular or patchy shadows. A hallmark of sarcoidosis is the presence of non-caseating granulomas found during biopsy, which helps differentiate it from other granulomatous diseases.

Key Clinical Features of Sarcoidosis

Pulmonary involvement occurs in over 90% of sarcoidosis cases, with symptoms ranging from mild cough and shortness of breath to progressive interstitial lung disease in advanced stages. Other signs include skin lesions such as erythema nodosum, eye inflammation (uveitis), and enlarged lymph nodes visible on chest imaging. While these findings can overlap with autoimmune conditions, the histological pattern remains a critical diagnostic clue.

Lupus: A Complex Autoimmune Disorder

In contrast, systemic lupus erythematosus (SLE), commonly known as lupus, is an autoimmune disease that can affect multiple organ systems. Its pulmonary manifestations are diverse and may include pleuritis, pulmonary hypertension, diffuse alveolar hemorrhage, and even pulmonary embolism due to hypercoagulability. Interstitial lung disease can also occur in lupus patients, creating potential diagnostic confusion with sarcoidosis.

Differential Diagnosis: Why Confusion Can Arise

Although sarcoidosis and lupus have distinct pathologies, certain clinical features can overlap. For example, both conditions may present with erythema nodosum-like rashes and generalized lymphadenopathy. In rare cases, patients might exhibit overlapping serological markers or systemic inflammation, making initial diagnosis challenging without thorough evaluation.

How Doctors Avoid Misdiagnosis

To prevent misdiagnosis, clinicians rely on a combination of imaging studies, laboratory tests, and tissue biopsies. The presence of non-caseating granulomas strongly supports sarcoidosis, whereas positive antinuclear antibodies (ANA), anti-dsDNA antibodies, and other immunological markers point more toward lupus. Additionally, patterns on high-resolution CT scans and response to treatment can further clarify the correct diagnosis.

Conclusion: Accurate Diagnosis Saves Time and Improves Outcomes

While sarcoidosis is generally not mistaken for lupus due to their differing underlying mechanisms and diagnostic criteria, vigilance is essential when symptoms overlap. Early and accurate differentiation through comprehensive testing ensures appropriate management and improves long-term prognosis for patients. Awareness of these similarities empowers both physicians and patients to seek precise diagnoses and tailored therapies.