A closer look at sarcoidosis and exposure

Sarcoidosis is an autoimmune disease in which granulomas can appear in many places in the body, such as in the lungs, skin, eyes and lymph nodes. It is a condition whose cause is unclear, but there are indications that exposure to metals and silica may play a role. These indications come from case descriptions and epidemiological studies. But little or no systematic research has been done to date.

Dusty work and sarcoidosis
Image by Вильнур Хаметов from Pixabay

Dutch study

Recently, a Dutch study (Beijer et al. 2020) was conducted in which a group of patients with sarcoidosis was compared with control subjects. Special attention was given to the work history and exposure at work. Patients from the outpatient clinic for Interstitial Lung Diseases in Nieuwegein with a diagnosis of sarcoidosis (256) were compared with patients who visited the same clinic for obstructive sleep apnea (73). External exposure does not seem to play a role in this condition.

There were no differences in age, gender and ethnicity between the groups of patients and controls. Only among the sarcoidosis patients were more people who had never smoked. Labor history information was collected using an online questionnaire. The professions listed were coded and an exposure exposure to silica and metals was estimated using a Job Exposure Matrix (JEM). Among sarcoidosis patients, 32,4% in the profession were exposed to silica and metals compared to 24,7% in the control group. But this difference was not significant (OR = 1,47; 95% CI 0.81 to 2,97)

Immune reactivity

Immune reactivity was tested to test the effect of exposure to metals and silica on the immune system. This is done with a Lymphocyte Proliferation Test (LPT) and special attention was paid to beryllium, aluminum, zirconium and silica. When performing the LPT on the participants' blood, not all tests proved useful for various reasons. It was also striking that the use of medication that inhibits the immune system was much higher in patients with sarcoidosis (45,5%) than in people in the control group (0%).

The blood was examined in 45 sarcoidosis patients exposed to metals and silica. This sample was chosen at random. The Lymphocyte Proliferation Test (LPT) investigated the effect of exposure to beryllium, aluminum, zirconium and silica. In addition to this group of exposed patients, 10 non-exposed sarcoidosis patients and 20 control subjects were also tested.

Positive tests

A positive LPT test (evidence of immune reactivity) was found in 7 (21,2%) sarcoidosis patients, but none of the controls. One patient tested positive for aluminum, three for beryllium, two for silica and two for zirconium. Remarkably, only 4 of the 26 exposed sarcoidosis patients were positive, compared to 3 of the 7 unexposed sarcoidosis patients.

The researchers state that this is the first study to combine exposure with lymphocyte proliferation tests for inorganic agents in sarcoidosis. No significant difference in exposure to metals and silica was found between patients and controls. However, immune reactivity to various antigens was only observed in sarcoidosis patients. It therefore seems that exposure to metals and / or silica plays a role in a subgroup of sarcoidosis patients.

JEM exposure does not predict

However, it appears not to be possible to make a prediction about immune reactivity on the basis of the work history linked to a JEM. Almost half of the patients with immune reactivity showed no evidence of exposure to metals or silica through the JEM. The method may still be too coarse to determine small differences in exposure. It is known from previous research that relatively low exposure may already be relevant for beryllium exposure.

Although the group in which immune reactivity has been tested is very small, it appears that in addition to the more well-known beryllium, exposure to silica, aluminum and zirconium can also lead to immune reactivity. It may be advisable to test all sarcoidosis patients to determine whether there may have been a reaction to metals or silica. Even when there are no direct indications of such exposure from the labor history.

Source

Beijer, E., Meek, B., Bossuyt, X., Peters, S., Vermeulen, R., Kromhout, H., & Veltkamp, ​​M. (2020). Immunoreactivity to metal and silica associates with sarcoidosis in Dutch patientsrespiratory research21(1), 141. https://doi.org/10.1186/s12931-020-01409-w

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