Rheumatism or rheumatic disorders are conditions causing chronic, often intermittent pain affecting the joints or connective tissue. Rheumatism does not designate any specific disorder, but covers at least 200 different conditions including arthritis and 'non-articular rheumatism', also known as 'regional pain syndrome' or 'soft tissue rheumatism'. Rheumatism or rheumatic disorders are conditions causing chronic, often intermittent pain affecting the joints or connective tissue. Rheumatism does not designate any specific disorder, but covers at least 200 different conditions including arthritis and 'non-articular rheumatism', also known as 'regional pain syndrome' or 'soft tissue rheumatism'. The term 'Rheumatic Diseases' is used in MeSH to refer to connective tissue disorders. The branch of medicine devoted the diagnosis and therapy of rheumatism is called rheumatology. Many rheumatic disorders of chronic, intermittent joint pain have historically been caused by infectious diseases. Their etiology was unknown until the 20th century and not treatable, like Lyme disease (in the Northern and Northeastern US), coccidiomycosis or Valley fever (in the Western US), and Chikungunya in India and a myriad of causes for postinfectious arthritis also known as reactive arthritis like, for example, the once very common rheumatic fever after Group A Streptococcus infection up to the rare Whipple's disease. Major rheumatic disorders currently recognized include Although these disorders probably have little in common in terms of their epidemiology, they do share three characteristics: they cause chronic, often intermittent pain, they are difficult to treat and are collectively very common.