Light micrograph of sarcoidosis, an immune system disorder characterized by tiny clusters of cells in various organs. The lumps are called granulomas, because they have the appearance of grains of sugar or sand. These granulomas can grow and aggregate, creating many small and large clumps. They appear most often in the lungs and lymph nodes (as is the case here). Too many of these clusters can impede an organs function, causing the symptoms associated with sarcoidosis. These symptoms can include fatigue, weight loss, aches and pains, arthralgia, and shortness of breath. Symptoms can occasionally appear suddenly but usually appear gradually. The clinical course generally varies and ranges from asymptomatic disease to a debilitating chronic condition that may lead to death.