Haemochromatosis

Haemochromatosis may be primary (caused by a hereditary error of metabolism that leads to increased absorption of iron from the gastrointestinal tract) or secondary (associated with an increased intake and accumulation of iron of known cause, such as alcoholic cirrhosis, multiple blood transfusions, refractory anaemia and chronic excess oral iron ingestion).

The joint abnormalities consist of (1) abnormal amounts of haemosiderin granules, and (2) calcium pyrophosphate dihydrate (CPPD) crystal deposition. Both iron and CPPD crystals may accumulate in the same joint. Inflammation of the synovial membrane is not a major feature of haemochromatosis, however. Chondrocalcinosis from CPPD crystal deposition may occur in the fibrocartilage and hyaline cartilage of the knee, symphysis pubis, wrist and intervertebral disc. Cartilaginous fibrillation and erosion may also be observed.

The bone abnormalities in haemochromatosis are similar to those noted in idiopathic CPPD crystal deposition disease (presence of bone eburnation and cysts and the absence of significant osteophyte formation).

On radiographs, osteoporosis may be seen in either the axial or the appendicular skeleton. In the spine, biconcave deformities or fish vertebrae identical to those occurring in other forms of osteoporosis occur. In the appendicular skeleton, diffuse osteoporosis has been seen. Chondrocalcinosis and arthropathy are also common, the latter resembling degenerative joint disease, with joint space narrowing, sclerosis and osteophytosis. As in idiopathic CPPD crystal deposition disease, the arthropathy involves unusual sites, large subchondral cystic lesions develop and uniform loss of articular space occurs. In haemochromatosis, however, there is greater predilection for the metacarpophalangeal joints, widespread wrist lesions are present, and the pattern of osteophytosis is unusual (beaklike osteophytes of the metacarpal heads) (Fig.1).

DR/RB