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.

[The presence of mycobacteria in bronchoalveolar lavage fluid from an immunocompetent patient does not necessarily imply tuberculosis]. / La présence de mycobactéries dans un LBA de sujet immunocompétent n'est pas synonyme de tuberculose.

Mycobacterium tuberculosis is the most frequently identified mycobacterium in the bronchoalveolar lavage fluid (BALF) of immunocompetent patients. Lung infections due to non-tuberculous mycobacteria (NTM) are rare in such patients and then often occur in the context of pre-existing chronic lung disease. We report the case of an immunocompetent 85-year-old woman without pre-existing lung disease in whom M. abscessus was recovered from BALF. Cytological examination of the BALF revealed an increased number of neutrophils and some acid-fast bacilli, all located within neutrophil cytoplasm. This case report contributes a cytological description of BALF in the context of M. abscessus infection, which is poorly detailed in the literature.