Joint space narrowing also follows a similar pattern in the two diseases. Both involve the radiocarpal and midcarpal compartments of the wrist with diffuse joint space narrowing and intra-articular and periarticular calcifications, which are not seen with osteoarthritis
One must, therefore, use other features to help differentiate the two. In hemochromatosis arthropathy, there is uniform loss of joint space at all metacarpophalangeal joints, including those of the ring and small fingers, while in calcium pyrophosphate dihydrate deposition disease, there is narrowing of predominantly the index and middle finger metacarpophalangeal joints.
In more advanced disease, other differences become apparent. Scapholunate dissociation is more common in advanced calcium pyrophosphate dihydrate deposition disease, while advanced hemochromatosis is more likely to have metacarpophalangeal joint narrowing in the absence of radioscaphoid narrowing.
Osteoporosis is usually a feature of hemochromatosis, but is usually not present in calcium pyrophosphate dihydrate deposition disease.