Intense Muscle Activity Due to Polymyositis Incidentally Detected in a Patient Evaluated for Possible Malignancy by FDG PET/CT Imaging

Abstract

A 42-year-old woman suffered shortness of breath and whole-body pain, more prominent in both thighs. After the initial assessment, a paraneoplastic syndrome was considered clinically, and FDG PET/CT was performed to search culprit malignancy. The images did not reveal any focal lesion typical of solid hypermetabolic malignancy. Instead, diffuse increased muscle activity was noted in most musculatures, with some focally intense. The findings were suggestive of polymyositis, which was subsequently confirmed.

Systemic Vasculitis Following SARS-CoV-2 mRNA Vaccination Demonstrated on FDG PET/CT: Reply

“…Typical FDG PET/CT findings in patients with polymyositis or focal myositis show intense muscle accumulation. 2,3 However, the present case lacked such findings in skeletal muscle. Muscle biopsy was performed from the left vastus lateralis muscle, which failed to show pathognomonic findings.…”

“…Myositis was also considered a differential diagnosis, but he did not have an elevated creatine kinase level (34 U/L). Typical FDG PET/CT findings in patients with polymyositis or focal myositis show intense muscle accumulation 2,3 . However, the present case lacked such findings in skeletal muscle.…”

Treatment-naïve idiopathic inflammatory myopathy: disease evaluation by fluorodeoxyglucose versus pyrophosphate

“…On the whole, there seems to be a wide distribution range of FDG uptake in IIM patients [25,26,30,31]. FDG PET/CT is sensitive but unspecific; the increased FDG uptake in skeletal muscles may be indicative of inflammation/injury, but also of physical activity right before or during the time from tracer injection to imaging, high insulin levels, and other reasons [42,43]. FDG was not previously compared directly with PYP in IMM patients, but it has been studied along with the PET bone tracer, fluorine-18-sodium fluoride (NaF), with characteristics similar to those of PYP for the detection and quantification of early-stage atherosclerosis [44][45][46].…”