Pathology-Sarcoidosis

I. Definition:

• Sarcoidosis is a multisystem inflammatory disease of unknown etiology characterized by the formation of granulomas (collections of immune cells) in various tissues.

II. Epidemiology:

• Prevalence: 10-20 cases per 100,000 individuals in the UK.
• Age of Onset: Peaks between 20-40 years old.
• Race: Individuals of African descent tend to experience more severe disease.

III. Etiology:

• Unknown. The underlying cause remains unidentified.

IV. Pathogenesis:

• The granulomatous inflammation is hypothesized to be a reaction to an unidentified antigen (foreign substance triggering an immune response). The exact antigen remains unknown.

V. Presentation:

• Multisystemic: Can affect virtually any organ, but most commonly involves lymph nodes, lungs, and skin.
• Acute Sarcoidosis: Sudden onset with symptoms like:
  • Erythema nodosum (skin inflammation)
  • Anterior uveitis (eye inflammation)
  • Seventh cranial nerve palsy (facial weakness)
  • Bilateral hilar lymphadenopathy (enlarged lymph nodes in the lungs - visible on chest X-ray)
• Chronic Sarcoidosis: Insidious onset with features such as:
  • Lupus pernio (facial skin lesions)
  • Pulmonary fibrosis (scarring of lung tissue)
  • Posterior uveitis (eye inflammation)

VI. Histopathology (Microscopic Examination):

• Non-necrotizing granulomas: The hallmark finding is the presence of granulomas that lack central cell death (necrosis).
• "Naked" granulomas: Sarcoid granulomas are typically well-circumscribed with minimal surrounding inflammatory cells, appearing "naked" under a microscope.
• Fibrosis: Variable degrees of fibrosis (scarring) may accompany the granulomas.
• Absence of other causes: Crucially, other explanations for the granulomas (infections, foreign bodies, tumors) must be ruled out.

VII. Prognosis:

• Acute Sarcoidosis: Generally has a favorable prognosis with spontaneous resolution within 1-2 years after diagnosis.
• Chronic Sarcoidosis: Carries a higher risk of complications, including progressive pulmonary fibrosis, potentially leading to respiratory failure and right ventricular failure (due to increased pressure in the pulmonary circulation).

Key Differences between Acute and Chronic Sarcoidosis: The table below summarizes the key distinctions: