Clinical value of a [18F]-FDG PET-CT muscle-to-muscle SUV ratio for the diagnosis of active dermatomyositis.

OBJECTIVE: To study a muscle-to-muscle standardised uptake value (SUV) ratio with FDG-PET/CT (FDG-PET) as a marker for the detection of disease activity in dermatomyositis (DM). METHODS: Patients with DM (n = 24) who met the European Neuro-Muscular Centre diagnostic criteria were retrospectively identified over a 3-year period through a national survey. Muscle biopsy was performed in all patients. Maximum SUV was measured in proximal muscles (SUVPROX) that had the highest radiotracer uptake on visual grading as well as in the musculus longissimus thoracis (SUVMLT), whereas mean SUV was measured for the liver (SUVLIV). Muscle-to-liver SUV ratios for either muscle group were compared and a SUVPROX/SUVMLT ratio was calculated. SUVPROX/SUVMLT of DM patients were compared with age- and sex-matched control subjects (n = 24) with melanoma who had received FDG-PET scans. RESULTS: DM patients presented with proximal and symmetrical muscle uptake. Differences in SUVPROX/SUVLIV and SUVMLT/SUVLIV ratios in DM subjects were significant (p < 0.001). SUVPROX/SUVMLT ratios in DM and their controls also differed significantly (p = 0.0012). The SUVPROX/SUVMLT ratio threshold between DM subjects and controls was 1.73 with a sensitivity of 50% (CI95%, 29.1 to 70.9%) and specificity at 83.3% (CI95%, 62.6 to 95.3%). When amyopathic DM patients were removed from the analysis, specificity was increased to 95% (CI95%, 75.1 to 99.9%) with a likelihood ratio of 10 and an AUC of 83.4% (CI95%, 71.4 to 95.4%). CONCLUSION: A muscle-to-muscle SUVPROX/SUVMLT ratio with a cut-off value of 1.73 in FDG-PET imaging might serve as a non-invasive marker to determine disease activity in dermatomyositis. KEY POINTS: • [18F]-FDG PET-scanner standardised uptake value (SUV) could reflect disease activity in dermatomyositis (DM). • A ratio of SUV in proximal muscles (SUVPROX) to SUV in musculus longissimus thoracis (SUVMLT) could be used to determine active DM. • Active disease is suspected for SUV PROX /SUV MLT ratios greater than 1.73.

Azacitidine-Induced Interstitial Pneumonitis.

Azacitidine is a demethylating and cytotoxic drug for the treatment of adult patients with (1) myelodysplastic syndromes, (2) chronic myelomonocytic leukemia, and (3) acute myeloid leukemia who are not eligible for induction treatment or hematopoietic stem cell transplantation. Widely described in the literature, the main adverse events are hematotoxicity, digestive toxicity, asthenia, cutaneous toxicity, and infections such as neutropenic sepsis and pneumonia. The pivotal phase III comparative and supporting studies did not point out interstitial pneumonitis as a significant adverse event. Rare clinical data from literature report interstitial lung disease secondary to azacitidine administration, which should therefore be considered as a serious potential adverse event. We, herein, report a case of an 86-year-old white woman with acute myeloid leukemia and azacitidine-induced interstitial pneumonitis.