The "whisker sign" as an indicator of ochronosis in skeletal scintigraphy.

A patient with alkaptonuria and ochronotic arthrosis was imaged twice with technetium-99m dicarboxypropane diphosphonate (99mTc-DPD)--once during a bout of arthritic knee pain and once when symptom-free. There was a marked accumulation of radioactivity in the large joints. During the episode of arthritis the knee joints had a higher uptake than when the patient was without symptoms. The intervertebral discs showed a high uptake which extended laterally from the axial vertebral column; the finding gave an impression of whiskers, and this "whisker sign" may be characteristic of ochronosis.