Musculoskeletal ImagingOxalosis
a disorder resulting from deposition of crystals of
calcium oxalate in tissues, characterized by destructive lesions in metaphyseal regions, discovertebral regions and sometimes joints.
Primary oxalosis
is transmitted in an autosomal recessive manner. The enzymatic defects in this form lead to overproduction of oxalate and its deposition in various tissues. The kidneys may be damaged (calcium oxalate nephrolithiasis and nephrocalcinosis), leading to progressive
renal failure and uraemia. Calcium oxalate also accumulates in the small arteries, eyes, soft tissues and bones. A foreign body giant cell reaction results in stimulation of new bone formation. Radiographically, primary oxalosis is characterized by the presence of
calculi and pyelonephritis. The kidneys may be small and contracted, with parenchymal
calcification. In addition, the
tubular bones may show irregular transverse sclerotic bands in the metaphyses of
tubular bones, which extend into the epiphyses; narrow translucent zones are seen at the level of the physis between the epiphyseal and metaphyseal components. In the humerus and femur, similar radiodense subchondral regions may resemble the findings of
ischaemic necrosis. In the
spine, sclerotic zones in the vertebral bodies simulate the appearance known as
rugger jersey spine typical of
renal osteodystrophy. Other abnormalities include a drumstick configuration of the metacarpal bones and, in chronic cases, widespread skeletal anomalies, pathologic fractures and
vascular and soft tissue
calcification. With massive deposits of calcium oxalate,
cystic bone lesions and deformities such as
protrusio acetabuli may occur.
Secondary oxalosis
which is more common than the primary form, may complicate other diseases or result from ingestion of substances that either contain the oxalate ion or are metabolized to oxalate (rhubarb, ethylene glycol). The crystals are deposited within the kidney or in other tissues. In bone, crystal accumulation is seen in the hypertrophic zone of the physes, the metaphyseal marrow, and areas of tissue necrosis associated with previous
fracture. Radiographs show radiodensity and a
cystic appearance owing to trabecular condensation. Joint manifestations include effusions, pain and stiffness; juxta-articular
osteoporosis and
calcification of the
capsule and
cartilage (
chondrocalcinosis) are observed.
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