How do I explain to people about my sarcoidosis?

Be honest. Sarcoidosis is a disease that can be serious involving multiple organs, most notably the lungs, but it can also cause kidney disease. It is treatable often with steroid medication. Chronic steroid therapy can cause changes in appearance such as a round face and thinning of the skin. Friends might show concern and you can tell them you need this medication to remain as healthy as possible.
Granulomas. It is an inflammatory condition related to the development of granuolmas throughout the body. The granuloma is a area of inflammation with the presence of of special cells: giant cells, monocytes, macrophages. These granulomas are the hallmark of sarcoidosis. Granulomas can be associated with other medical conditions including chronic infections are these need to be searched for in diagnosis.