Sarcoidosis

Basics

Description

  • Disorder, sometimes chronic and progressive, that primarily affects the lungs but can be multisystem
  • Characterized by local accumulation of monocytes, lymphocytes, and phagocytes that form nonnecrotic and noncaseating epithelioid granulomas
  • Symptoms mainly due to organ dysfunction due to disruption of local tissue architecture
  • Vitamin D (calcitriol) level may be increased due to increased production from granulomatous tissue:
    • Increased expression of 1-alpha-hydroxylase, converts precursors to vitamin D
    • leads to secondary hypercalcemia
  • ACE levels often elevated, blood pressure response variable
  • Prevalence 10–40/100,000 in the US and Canada:
    • People of African descent higher predominance
    • 2.4% lifetime risk to blacks, whites 0.85%
  • Bimodal distribution of onset, typically young adults (male > female) or adults 40–55 yr old (female > male)
  • Incidental diagnosis in more than half of cases

Etiology

  • Unclear, but consistent with antigen-driven pattern
  • Antigen suspects include:
    • Remnants of P. acnes and non-Tb Mycobacteria
    • Pesticides
  • Environmental factors likely contribute:
    • Higher geographic latitudes (eg, Scandinavia)
    • Work in health care settings
    • Increase noted in 9/11 responders
  • Familial clustering suggests genetic component
  • CD4 predominant T-cells
  • Initial mediation by IFN-γ, TNF, IL-2, IL-12 cytokines, then profibrotic TGF-β, PDGF, IGF-1

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