Porth's Essentials of Pathophysiology, 4e

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Disorders of the Skeletal System: Metabolic and Rheumatic Disorders

C h a p t e r 4 4

can be excreted easily. Pegloticase is an infusible uricase agent that works rapidly to reduce serum uric acid and tophaceous deposits of urate. Prophylactic colchicine may be used between gout attacks.

Rheumatic Diseases in Children and the Elderly Rheumatic diseases differ among children, adults, and the elderly in terms of diagnosis, impact of activities, and availability of treatment modalities. These con- ditions, which affect not only the child but also the family, can seriously impact a child’s growth and devel- opment, limit their participation in childhood activities, and require an extensive plan of drug treatment and rehabilitation. Weakness and gait disturbance that often accompany the rheumatic diseases in the elderly can contribute to the likelihood of falls and fracture, causing suffering, increased health care costs, further loss of independence, and the potential for a decreased life span. Rheumatic Diseases in Children Children can be affected by many of the same types of rheumatic diseases that occur in adults. About 1 child in every 1000 develops some type of juvenile arthritis. 69 It can affect a single joint or multiple joints, and cause systemic manifestations such as fevers, rash, and eye dis- orders. Rheumatic disorders of children include juvenile idiopathic arthritis, juvenile spondyloarthropathies, and juvenile dermatomyositis. Juvenile Idiopathic Arthritis Juvenile idiopathic arthritis (JIA), formerly known as juvenile rheumatoid arthritis , is the most common form of childhood arthritis, and one of the most common forms of chronic disease in chiddren. 70–74 The disorder joint structures. Risk factors for OA progression include older age, multiple joint involvement, neuropathy, and, for knees, obesity.The joint changes associated with OA, which include progressive loss of articular cartilage and subchondral bone, result from inflammatory changes that occur when cartilage tries to repair itself. ■■ Gout is a crystal-induced arthropathy caused by the presence of monosodium urate crystals in the joint cavity. It includes acute gouty arthritis with recurrent attacks of articular and periarticular inflammation, and the accumulation of crystalline deposits, called tophi, in articular surfaces, bones, and soft tissue surrounding joints.The disorder is accompanied by hyperuricemia, which results from overproduction of uric acid or from the reduced ability of the kidney to rid the body of excess uric acid.

SUMMARY CONCEPTS

■■ Systemic autoimmune rheumatic disorders are a group of chronic disorders with overlapping symptoms that are characterized by diffuse inflammatory lesions and progressive changes in connective tissue. ■■ Rheumatoid arthritis (RA) is a chronic systemic inflammatory disorder affecting multiple joints. Joint involvement, which is symmetric, begins with inflammatory changes of the synovium and formation of a destructive granulation tissue called pannus that leads to joint instability and eventual deformity. ■■ Systemic lupus erythematosus is a chronic autoimmune disorder that affects multiple body systems, including the musculoskeletal system, skin, kidneys, cardiovascular system, hematologic system, and central nervous system.There is an exaggerated production of autoantibodies, which interact with antigens to produce an immune complex.These immune complexes produce an inflammatory response in affected tissues. ■■ Systemic sclerosis is an autoimmune disorder of connective tissues. It causes extensive fibrosis of many body organs and systems including the sheaths or fascia covering tendons and muscles. ■■ The seronegative spondyloarthropathies, which include ankylosing spondylitis, reactive arthropathies, and psoriatic arthritis, affect the axial skeleton, particularly the spine. The inflammatory process associated with the disorders commonly affects areas where ligaments and tendons attach to bone. Ankylosing spondylitis, which is characterized by bilateral sacroiliitis and loss of motion in the spinal column, is considered a prototype of this classification category. Although the cause of the disorders is unknown, there is a striking association between the HLA-B27 antigen and development of the spondyloarthropathies. ■■ Osteoarthritis (OA), often referred to as “wear- and-tear” arthritis, is a slowly destructive disorder of the articular cartilage. It can occur as a primary idiopathic disorder or as a secondary disorder due to congenital or acquired defects in