ABSTRACT
A granuloma is an organized collection of macrophages, known as epithelioid cells, which fuse to form multinucleated giant cells. Sarcoidosis is a systemic granulomatous condition of unknown aetiology which may affect any part of the body, but most frequently involves the lungs and intra-thoracic lymph nodes, in over 90 percent of cases. Sarcoidosis is a condition of young adults with a peak onset between the third and fourth decades. The aetiology of sarcoidosis remains unknown, but theories suggest an immunological response to an unidentified antigen in genetically predisposed individuals. Sarcoidosis is a multisystem disease; the reported distribution of clinical manifestations tends to reflect the bias of the treating physician. No test is pathognomonic for sarcoidosis. Magnetic resonance imaging (MRI) of the brain may show granulomatous involvement of the basal meninges. Granulomatosis with polyangiitis (GPA) is a systemic condition characterized by granulomatous inflammation of the respiratory tract and necrotizing vasculitis affecting small- to medium-sized vessels with focal or proliferative glomerulonephritis.
