Cardiac and skeletal muscle scintigraphy in dermato- and polymyositis: Clinical implications

To determine the role of scintigraphy in the detection of skeletal and cardiac involvement in dermato- and polymyositis (DM/PM), we studied 30 patienls with a confirmed diagnosis of DM/PM (23 females, 7 males; mean age: 35 years). Technetium-99m pyrophosphate (Tc-99m-PYP) and gallium-67 scans showed similar sensitivity, specificity and accuracy in the detection of skeletal muscle involvement when compared with serum enzymes (70%, 100% and 80%, respectively). Compared with the clinical parameters, Tc-99m-PYP showed 70% and Ga-67 65% accuracy. Abnormal PYP cardiac uptake was observed in 57% of patients, whereas abnormal Ga-67 cardiac uptake was seen in only 15%. Electrocardiography was abnormal in 40%, rest gated blood pool study in 23%, and chest X-ray in 13%. In conclusion, both Tc-99m-PYP and Ga-67 can be useful in the detection of the active phase of muscle disease. However, Tc-99m-PYP seems to be more effective than Ga-67 in the early diagnosis of cardiac involvement.