What is Sarcoidosis?

Background

Sarcoidosis is a multisystem granulomatous disease.

This means that many parts of the body are affected by granulomas. A granuloma is a mass or nodule made up of chronic inflammatory cells, which have formed in the body as a response to either foreign substances (such as macrophages and cells derived from them, e.g. giant cells) or as an immunological reaction to a particulate, poorly degradable antigen (macrophages etc + lymphocytes known as immune granuloma). Sarcoidosis granulomas have the characteristics of immune granuloma, as does tuberculosis.

The disease shares some of the features of tuberculosis (TB) but the causes and treatment are different. Also, whereas in tuberculosis the granulomas are characteristically caseating, in sarcoidosis they are non caseating. (Caseation is a process which occurs in the body, the result of tissue death. It comes from the Latin word meaning “cheese”. The dead tissue becomes soft, dry and cheese- like).

A condition in which non-caseating granulomas occur in at least 2 organs is likely to be sarcoidosis.

The granulomas can form in any tissue of the body, but mostly affect the -:

• lymph nodes in the hila of the lungs,
• the lung tissue itself,
• skin,
• eyes.

Less commonly, granulomas can form in the -:

• spleen,
• bones,
• muscles,
• joints,
• heart,
• liver,
• kidneys,
• nervous system.

The granulomas may become scarred or disappear.

Causes

Other than exposure to beryllium (a toxic and possibly carcinogenic metallic mineral), which is uncommon, the cause of the disease is unknown.

Pathogenesis (The development of the disease)

The granuloma is the manifestation of the particular sort of immunological reaction which is occurring.

Whom Does It Affect?

It usually affects young adults, between the ages of 20 to 40 with a female preponderance. Though present worldwide, it is commoner in colder countries like Scandanavia and Ireland. It affects around 19 persons per 100,000 in the UK.

The course of the disease tends to be more severe in racial groups such as American black patients than in Caucasians. There is a geographical variation with countries like Japan less commonly affected. Healthcare workers have an increased risk of developing the disease. The reasons are not clear but may relate to increased opportunity for the disease to be ascertained.

A disease with almost identical clinical and pathological manifestations can occur in response to beryllium exposure, (chronic beryllium disease). An individual with apparent sarcoidosis who works in industry should have a detailed occupational exposure history to see if there has been any beryllium exposure. Certain genetic factors may be associated with particular manifestations of the disease.

Amended November 2008