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Findings: Dense transverse metaphyseal bands.

Diagnosis:: Metaphyseal Bands ("lead lines").

Discussion: Dense transverse metaphyseal bands (more dense than cortical bone) occur with chronic lead poisoning. Lead deposition is a partial factor for increased density, but the primary cause is increased calcium deposition, with thicker and more numerous trabeculae. These metaphyseal bands, or "lead lines," usually do not occur until blood levels reach 70-80 mg/dl, and also are not an early manifestation of lead intoxication.

Lead lines are most prominent at the knees, but can also be seen in the wrist, any other long bone metaphysis, and in the axial skeleton. Single transverse lines predominate but multiple bands may be seen with episodic lead poisoning.

The band migrates into the substance of bone at a rate that correlates with bone growth. If normal blood lead levels are maintained, the lead lines gradually decrease in radiodensity and disappear in about 4 years.

The most common cause of a dense metaphyseal band is exuberant calcification of the zone of provisional calcification, a normal variant. It is often seen in normal children, especially following sunlight exposure after winter. Dense metaphyseal bands are also seen with heavy metal poisoning, hypervitaminosis D, and the healing stages of leukemia, rickets, and scurvy.

References:
1. Diagnosis of Bone and Joint Disorder, 2nd Ed., Resnick, 1988.

2. Differential Diagnosis in Pediatric Radiology, L. Swischuk, 1984.

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