Gallium-67 scintigraphy in macrophagic myofasciitis

To evaluate gallium-67 (67Ga) uptake and the value of 67Ga scintigraphy for diagnosis of macrophagic myofasciitis (MMF), a recently identified inflammatory myopathy.

Twelve consecutive patients with MMF confirmed by muscle biopsy, 10 with polymyositis, 10 with sarcoidosis, 8 with fibromyalgia, and 10 with lymphoma without muscle symptoms (serving as normal controls for muscle) were included. Patients received 1.8 MBq 67Ga per kg body weight by intravenous injection, and scintigraphy was performed with a 2-head gamma camera. The various views were acquired for the 3 main photopeaks of 67Ga 48 hours after infusion, and were analyzed in 2 blinded experiments by nuclear physicians. A semiquantitative scale was used to compare the uptake of 67Ga in the vascular soft tissue background with that in the muscles or joints of MMF patients, and with that in the normal controls.

The MMF patients (4 men and 8 women, mean +/- SD age 47.8 +/- 8.7 years) had chronic myalgia (n = 11; predominantly in the lower limbs), asthenia (n = 10), arthralgia (n = 7), mild muscle weakness (n = 5), and high serum creatine kinase levels (n = 6). All MMF patients had significantly higher levels of 67Ga uptake in the muscle and para-articular areas than that recorded for the soft tissue background and for the controls. Muscle uptake was bilateral, symmetric, and homogeneous, and predominantly localized in the legs. No linear enhancement corresponding to fascias or synovial involvement was observed. In patients with polymyositis, symmetric, but heterogeneous, 67Ga uptake was observed in muscle, but not in the fascia. In patients with sarcoidosis, 67Ga uptake was nodular and heterogeneous in muscle, was not detected in the fascia, and was suggestive of synovial involvement in the joints. The uptake of 67Ga in fibromyalgic patients was similar to that in normal controls and to that in the soft tissue background.

MMF is a new condition involving characteristic changes that can be detected by deltoid muscle biopsy. It usually manifests as a weakly specific, chronic arthromyalgic syndrome that predominates in the lower limbs. 67Ga scintigraphy is a noninvasive method that may make it easier to differentiate MMF from fibromyalgia and sarcoidosis.