A Rare Case of Diffuse Pyomyositis on Gallium Scintigraphy
A 61 year old diabetic female presented with a 1 week history of back pain radiating down both legs, associated with chills, vomiting, confusion, diffuse muscular tenderness and rash. Her CRP level was 481, consistent with the presence of an acute inflammatory reaction. Shortly after, she became hypoxic, hypotensive and oliguric. She was transferred to ICU with multi-organ failure. Her blood cultures were positive for staphylococcus aureus and IV antibiotics commenced. Abscess, septic arthritis, osteomyelitis and myositis were all suspected.
A whole body bone scan showed diffuse hyperaemia in the left arm and mildly increased uptake in the right sacro-iliac joint, but no evidence of osteomyelitis. A CT scan of the abdomen showed changes of myositis in the lower back muscles. A gallium scan demonstrated uptake throughout the proximal and distal muscles of the upper and lower limbs. These findings are consistent with widespread myositis (inflammation of the muscles), specifically pyomyositis in this case. The most intense uptake was in the right shoulder, where the patient subsequently suffered a ruptured supraspinatus muscle resulting from an abscess.
Pyomyositis is a bacterial infection of the skeletal muscles, most common in tropical areas. In temperate climates it is extremely rare, and typically occurs in people with immune deficiencies, most commonly HIV, diabetes or malignancy.
The whole body gallium images confirmed the diagnosis of pyomyositis and revealed the widespread nature of her condition. This case illustrates the importance of gallium imaging in both diagnosis and establishing the extent of pyomyositis.