2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups.

OBJECTIVE: To develop and validate new classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIM) and their major subgroups. METHODS: Candidate variables were assembled from published criteria and expert opinion using consensus methodology. Data were collected from 47 rheumatology, dermatology, neurology and paediatric clinics worldwide. Several statistical methods were used to derive the classification criteria. RESULTS: Based on data from 976 IIM patients (74% adults; 26% children) and 624 non-IIM patients with mimicking conditions (82% adults; 18% children), new criteria were derived. Each item is assigned a weighted score. The total score corresponds to a probability of having IIM. Subclassification is performed using a classification tree. A probability cut-off of 55%, corresponding to a score of 5.5 (6.7 with muscle biopsy) 'probable IIM', had best sensitivity/specificity (87%/82% without biopsies, 93%/88% with biopsies) and is recommended as a minimum to classify a patient as having IIM. A probability of ≥90%, corresponding to a score of ≥7.5 (≥8.7 with muscle biopsy), corresponds to 'definite IIM'. A probability of <50%, corresponding to a score of <5.3 (<6.5 with muscle biopsy), rules out IIM, leaving a probability of ≥50 to <55% as 'possible IIM'. CONCLUSIONS: The European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for IIM have been endorsed by international rheumatology, dermatology, neurology and paediatric groups. They employ easily accessible and operationally defined elements, and have been partially validated. They allow classification of 'definite', 'probable' and 'possible' IIM, in addition to the major subgroups of IIM, including juvenile IIM. They generally perform better than existing criteria.

Selective pattern of muscle involvement seen in distal muscular dystrophy associated with anoctamin 5 mutations: a follow-up muscle MRI study.

Anoctaminopathy is a new muscular dystrophy caused by mutations in the ANO5 gene. ANO5 mutations cause distal and proximal phenotypes. We report here a follow-up muscle MRI study on five patients affected by distal form of anoctaminopathy. T1 weighted scans showed subsequent involvement of gastrocnemius medialis and soleus, hip adductors, hamstrings, gastrocnemius lateralis and quadriceps muscles, and later on tensor fascia lata, gluteus minimus and biceps brachii muscles, respectively. The STIR weighted images showed in the early stages widely distributed hyperintense signals, myoedema, in the adductors, hamstrings, and quadriceps muscles, which at that time have normal T1 signals. All patients showed asymmetry of muscle involvement both clinically and on muscle imaging. The progression of muscle involvement was relatively slow. We conclude that the pattern of muscle involvement seen in patients with distal myopathy with anoctamin 5 mutations (MMD3) is typical and can thus be useful during the differential diagnosis process allowing for a more targeted molecular approach.