17th January 2024

Background

Epidemiology

Sarcoidosis is a multi-system disorder which can affect most organs in the body. Pulmonary sarcoidosis is the most common presentation, affecting up to 90% of patients with the disease and accounting for a large proportion of morbidity and mortality. Prevalence of sarcoidosis in the UK is around 175 cases per 100,000 population, affecting males and females equally. Most people are diagnosed between the ages of 30 and 60. There is a higher prevalence among people of Irish and Afro-Caribbean descent, and therefore, across the UK, cases are most concentrated in London, Scotland and Northern Ireland due to the prominence of these population groups in those regions (1).

Pathophysiology

The exact aetiology of sarcoidosis is unclear, although it is characterised by the accumulation of non-caseating granulomas in various tissues, including, but not limited to, the lungs. The granulomata are comprised of accumulated macrophages, CD4-positive T-lymphocytes and multinucleated giant cells. There is an associated increased production of cytokines such as tumour necrosis factor alpha, (TNF-α), interferon-gamma (IF-γ), interleukin-2 (IL-2) and transforming growth factor beta (TGF-β), mediating a widespread inflammatory process. These granulomata have a propensity for the thoracic lymph node sites, but can also form in the lung parenchyma (2).