Introduction

Arthropathy is one of the common and early clinical manifestations of hemochromatosis. Described in 1964, hemochromatosis arthropathy was described as a form of arthritis with distinctive synovial membrane changes and characteristic joint distribution and radiographic findings. It has been increasingly recognized as a clinical feature of hemochromatosis that sometimes leads to early diagnosis and treatment before irreversible iron-associated injury occurs to the liver and other organs.

Pathogenesis

Morphologic studies of joints affected with hemochromatosis arthropathy reveal iron deposits in the synovium and cartilage and degenerative changes in the articular cartilage. Iron deposition is generally most prominent in the synovial lining layer (Fig. 24.1). Proliferation of the synovial lining cells is mild or moderate, and characteristically there is little deeper inflammation (Fig. 24.1). By electron microscopy (EM), aggregates of ferritin are visualized predominantly in the synovial type B (synthetic) cells and, to a lesser extent. in the synovial type A (phagocytic) cells, (Fig. 24.2). Nearly all iron detected by EM and light microscopy is intracellular, and most cells that contain iron appear intact. Ferritin granules occur diffusely throughout the cytoplasm and formaggregates between the cisterns of rough endoplasmic reticulum. When iron loading is severe, macrophages also contain deposits. However, the presence of stainable iron in joint tissues is also found in rheumatoid arthritis, osteoarthritis, pigmented villonodular synovitis, hemophilia, and hemarthrosis. In these latter disorders, iron deposition tends to occur more in deep macrophages, although increased iron may also occur in type B cells. In patients with hemochromatosis, iron deposition in chondrocytes of the articular cartilage is a common but not invariable finding, and ferritin particles occur in intact and degenerating chondrocytes (Fig. 24.3).