Rheumatic diseases are a group of diseases that affect bones, joints and their surrounding soft tissues (e.g., muscles, bursae, tendons, fascia, nerves, etc.) in general. Their etiology can be infectious, immune, metabolic, endocrine, degenerative, geoenvironmental, genetic, tumorigenic, etc. They can be systemic or limited; they can be psychiatric or functional. Diffuse connective tissue diseases, including various arthritis, are an important part of rheumatic diseases, but rheumatic diseases are not limited to diffuse connective tissue diseases. The pathological changes of rheumatic diseases are both inflammatory and non-inflammatory, and different diseases often involve different target tissues, thus constituting disease-specific clinical manifestations. Among the inflammatory changes, most of the diseases are due to aggressive immune reactions, except for gout, which is an inflammatory manifestation due to deposition of uric acid nodules in the joints. The manifestation is the infiltration and aggregation of large numbers of lymphocytes, macrophages, and plasma cells in the tissue of the selenium. Vascular inflammation is another common, common pathological change in rheumatic diseases. Vascular inflammation leads to thickening of the vessel wall, narrowing of the lumen, local tissue ischemia, and therefore to the corresponding clinical manifestations. The main pathological features of common rheumatic diseases are as follows: rheumatoid guanitis as synovitis; ankylosing spondylitis as attachment point inflammation; systemic lupus erythematosus as small vessel inflammation; dry syndrome as salivary gland and lacrimal gland inflammation; polymyositis/dermatomyositis as myositis; vasculitis as large, medium, small arteriosclerosis and phlebitis; osteoarthritis as articular cartilage degeneration; and systemic sclerosis as subcutaneous fibrous tissue hyperplasia. The probability of occurrence of the main connective tissue diseases in children in the 48934 consecutive cases registered in the database of the study of rheumatic diseases in children is as follows: rheumatoid arthritis 65.2%, systemic lupus erythematosus 10.7%, dermatomyositis 5.8%, systemic sclerosis 0.8%, limited sclerosis 3%, polyarteritis nodosa 0.4%, Kawasaki disease 2.3%, allergic purpura 7.4%, and Other vasculitis 4.3%. Juvenile rheumatoid arthritis is the most common chronic arthritis in children and is one of the leading causes of functional impairment and blindness in children. The impact of rheumatic fever in children should also be noted in China. In addition, 10% to 20% of school-age children may present with growing pains. Among 48934 consecutive patients registered in the Pediatric Rheumatology Research Database, the probability of occurrence of major connective tissue diseases in children was as follows: rheumatoid arthritis 65.2%, systemic lupus erythematosus 10.7%, dermatomyositis 5.8%, systemic sclerosis 0.8%, limited sclerosis 3%, polyarteritis nodosa 0.4%, Kawasaki disease 2.3%, allergic purpura 7.4%, and Other vasculitis 4.3%. Juvenile rheumatoid arthritis is the most common chronic arthritis in children and is one of the leading causes of functional impairment and blindness in children. The impact of rheumatic fever in children should also be noted in China. In addition, 10% to 20% of school-age children may develop growing pains.