What is sarcoidosis?

Understanding Sarcoidosis: A Simple Explanation

Sarcoidosis is a chronic multi-system inflammatory disease of unknown cause characterized by the formation of non-caseating granulomas that can affect multiple organs, most commonly the lungs and lymph nodes. 1

What is Sarcoidosis?

Sarcoidosis is an inflammatory disorder where the immune system forms clusters of immune cells called granulomas in various organs throughout the body. These granulomas are:

• Non-caseating (they don't have a cheese-like center of dead cells)
• Well-formed with concentric layers of immune cells
• Typically composed of macrophages, multinucleated giant cells, and T lymphocytes 1

Who Gets Sarcoidosis?

Sarcoidosis affects people worldwide, but with varying frequency:

• More common in northern Europe (Sweden, Iceland) with 20/100,000 population
• Less common in Japan (1.3/100,000)
• In the United States, more prevalent in African Americans (35.5/100,000) than whites (10.9/100,000)
• Twice as common in women than men
• Usually affects people in their 30s-40s, with a second peak in women aged 45-65 1

What Causes Sarcoidosis?

The exact cause remains unknown, but current understanding suggests:

• An exaggerated immune response to an unknown antigen
• Possible triggers include:
  • Infectious agents (mycobacteria, propionibacteria)
  • Environmental exposures (beryllium, zirconium)
  • Other substances (pine pollen, peanut dust)
• Genetic predisposition likely plays a role
• Involves T-cell mediated immune responses with CD4+ T cell accumulation 1, 2

Common Symptoms and Organ Involvement

Sarcoidosis can affect almost any organ, but most commonly involves:

1. Lungs and Lymph Nodes (up to 95% of cases)

   • Shortness of breath
   • Dry cough
   • Chest pain

2. Skin

   • Lupus pernio (purple lesions on face/ears)
   • Erythema nodosum (painful red bumps on shins)

3. Eyes

   • Uveitis
   • Scleritis
   • Vision problems

4. Upper Respiratory Tract (3-4% of cases)

   • Nasal congestion and blockage (90% of those with nasal involvement)
   • Crusting (66%)
   • Bleeding (40%)

5. Other Organs

   • Heart: arrhythmias, heart failure
   • Nervous system: facial nerve paralysis
   • Liver/spleen enlargement
   • Kidneys: hypercalcemia, kidney stones 1, 3

How is Sarcoidosis Diagnosed?

Diagnosis is based on three major criteria:

1. Compatible clinical presentation

   • Certain presentations are highly specific:
     • Löfgren's syndrome (fever, bilateral hilar lymphadenopathy, erythema nodosum)
     • Lupus pernio (specific skin lesions)
     • Bilateral hilar lymphadenopathy without B symptoms (fever, night sweats, weight loss)

2. Evidence of non-caseating granulomas in tissue samples

3. Exclusion of alternative causes of granulomatous disease 1

Common diagnostic tests include:

• Chest X-ray or CT scan (bilateral hilar lymphadenopathy is classic)
• Biopsy of affected tissue
• Blood tests (may show elevated ACE levels in 34-60% of patients)
• Pulmonary function tests
• Specialized imaging (PET scans, MRI for cardiac/neurological involvement) 1, 4

Disease Course and Prognosis

The course of sarcoidosis varies greatly:

• Many patients (30-80% of early stage cases) experience spontaneous remission
• About 10-40% develop chronic or progressive disease
• Mortality rate is approximately 7% over 5 years
• Most deaths (60%) are due to sarcoidosis itself, with up to 80% of these from advanced cardiopulmonary failure 2

Treatment Approaches

Treatment is typically reserved for symptomatic patients or those with progressive disease:

1. First-line treatment: Oral corticosteroids (prednisone 20-40mg daily)

   • Used for 6-18 months with gradual tapering
   • For symptomatic patients with parenchymal infiltrates and abnormal lung function

2. Second-line treatments: Immunosuppressive agents

   • Methotrexate
   • Azathioprine
   • Used when prolonged steroids are needed or side effects occur

3. Third-line treatments: Biologic agents

   • Anti-TNF medications
   • Used for refractory cases 2

Important Considerations

• Despite treatment, relapse rates range from 13% to 75%
• Regular monitoring is essential, especially for lung function and cardiac involvement
• The disease can be unpredictable, with periods of activity and remission
• Quality of life issues, particularly fatigue, often require specific management 2, 5

Understanding sarcoidosis requires recognizing its multi-system nature and variable presentation, which can make diagnosis challenging but essential for proper management.