ARTHRITIS ASSOCIATED WITH SYSTEMIC DISEASE
ARTHROPATHY OF ACROMEGALY
Acromegaly is the result of excessive production of growth hormone by an adenoma in the anterior pituitary gland (Chap. 383). The excess of growth hormone along with insulin-like growth factor I stimulates proliferation of cartilage, periarticular connective tissue, and bone, resulting in several musculoskeletal problems, including osteoarthritis, back pain, muscle weakness, and carpal tunnel syndrome.
Osteoarthritis is a common feature, most often affecting the knees, shoulders, hips, and hands. Single or multiple joints may be affected. Hypertrophy of cartilage initially produces radiographic widening of the joint space. The newly synthesized cartilage is abnormally susceptible to fissuring, ulceration, and destruction. Ligamental laxity of joints further contributes to the development of articular discomfort and osteoarthritis. Cartilage degrades, the joint space narrows, and subchondral sclerosis and osteophytes may develop. Joint examination reveals crepitus and laxity. Joint fluid is noninflammatory. Calcium pyrophosphate dihydrate crystals are found in the cartilage in some cases of acromegaly arthropathy and, when shed into the joint, can elicit attacks of pseudogout (calcium pyrophosphate arthropathy). Chondrocalcinosis may be observed on radiographs. Back pain is extremely common, perhaps as a result of spine hypermobility. Spine radiographs show normal or widened intervertebral disk spaces, hypertrophic anterior osteophytes, and ligamental calcification. The latter changes are similar to those observed in patients with diffuse idiopathic skeletal hyperostosis. Dorsal kyphosis in conjunction with elongation of the ribs contributes to the development of the barrel chest seen in acromegalic patients. The hands and feet become enlarged as a result of soft tissue proliferation. The fingers are thickened and have spadelike distal tufts. One-third of patients have a thickened heel pad. Approximately 25% of patients exhibit Raynaud’s phenomenon. Carpal tunnel syndrome occurs in about half of patients. The median nerve may become compressed by excess connective tissue in the carpal tunnel. Patients with acromegaly may develop proximal muscle weakness, which is thought to be caused by the effect of growth hormone on muscle. Serum muscle enzyme levels and electromyographic findings are normal. Muscle biopsy specimens contain muscle fibers of varying size without inflammation.
ARTHROPATHY OF HEMOCHROMATOSIS
Hemochromatosis is a disorder of iron storage. Absorption of excessive amounts of iron from the intestine leads to iron deposition in parenchymal cells, which results in impairment of organ function (Chap. 414). Symptoms of hemochromatosis usually begin between the ages of 40 and 60 but can appear earlier. Arthropathy, which occurs in 20–40% of patients, usually begins after the age of 50 and may be the first clinical feature of hemochromatosis. The arthropathy is an osteoarthritis-like disorder affecting the small joints of the hands and later the larger joints, such as knees, ankles, shoulders, and hips. The second and third metacarpophalangeal joints of both hands are often the first and most prominent joints affected; this clinical picture may provide an important clue to the possibility of hemochromatosis ...