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Simple and aneurysmal bone cysts are benign lytic bone lesions, usually encountered in children and adolescents. Simple bone cyst is a cystic, fluid-filled lesion, which may be unicameral (UBC) or partially separated. UBC can involve all bones, but usually the long bone metaphysis and otherwise primarily the proximal humerus and proximal femur. The classic aneurysmal bone cyst (ABC) is an expansive and hemorrhagic tumor, usually showing characteristic translocation. About 30% of ABCs are secondary, without translocation; they occur in reaction to another, usually benign, bone lesion. ABCs are metaphyseal, excentric, bulging, fluid-filled and multicameral, and may develop in all bones of the skeleton. On MRI, the fluid level is evocative. It is mandatory to distinguish ABC from UBC, as prognosis and treatment are different. UBCs resolve spontaneously between adolescence and adulthood; the main concern is the risk of pathologic fracture. Treatment in non-threatening forms consists in intracystic injection of methylprednisolone. When there is a risk of fracture, especially of the femoral neck, surgery with curettage, filling with bone substitute or graft and osteosynthesis may be required. ABCs are potentially more aggressive, with a risk of bone destruction. Diagnosis must systematically be confirmed by biopsy, identifying soft-tissue parts, as telangiectatic sarcoma can mimic ABC. Intra-lesional sclerotherapy with alcohol is an effective treatment. In spinal ABC and in aggressive lesions with a risk of fracture, surgical treatment should be preferred, possibly after preoperative embolization. The risk of malignant transformation is very low, except in case of radiation therapy.

Juvenile idiopathic arthritis (JIA) is characterized by synovial inflammation, with potential risk of developing progressive joint destruction. Personalized state-of-the-art treatment depends on valid markers for disease activity to monitor response; however, no such markers exist. To evaluate the reliability of scoring of carpal bone erosions on MR in children with JIA using two semi-quantitative scoring systems. A total of 1,236 carpal bones (91 MR wrist examinations) were scored twice by two independent pediatric musculoskeletal radiologists. Bony erosions were scored according to estimated bone volume loss using a 0–4 scale and a 0–10 scale. An aggregate erosion score comprising the sum total carpal bone volume loss was calculated for each examination. The 0–4 scoring system resulted in good intra-reader agreement and moderate to good inter-observer agreement in the assessment of individual bones. Fair and moderate agreement were achieved for inter-reader and intra-reader agreement, respectively, using the 0–10 scale. Intra- and particularly inter-reader aggregate score variability were much less favorable, with wide limits of agreement. Further analysis of erosive disease patterns compared with normal subjects is required, and to facilitate the development of an alternative means of quantifying disease.

Introduction Les myopathies inflammatoires de l’enfant sont un groupe tres heterogene de pathologies tant sur le plan clinique que anatomopathologique ou biologique. L’objectif de ce travail est de colliger des cas pediatriques de myosite de chevauchement afin d’ameliorer leur description et leur classification. Materiel et methodes Etude retrospective de patients suivis a l’hopital Necker-Enfants–Malades de 2002 a 2014, porteurs de myosite de chevauchement definie par l’association d’une myosite inflammatoire et de signe cliniques et/ou biologiques de connectivite. Sont repris la presentation clinique, les elements biologiques, histologiques (biopsies musculaires) et radiologiques (IRM) au diagnostic, les prises en charge therapeutiques et l’evolution. Resultats Vingt patients ont ete inclus, 3 garcons et 17 filles, d’âge median de 9 ans 5 mois [3 ans 9 mois–14 ans 1 mois]. Au diagnostic une myosite est presente chez tous les patients associee a une polyarthrite (n = 7), un syndrome de Raynaud (n = 4), une dyskinesie œsophagienne (n = 2), une atteinte pulmonaire definie par un syndrome interstitiel a l’imagerie ou DLCO Discussion Ce travail constitue la premiere etude de myosites de chevauchement a debut pediatrique. Quatre patients sur 20 ne repondent pas aux criteres classiques proposes par Troyanov pour les formes adultes mais leur presentation et evolution sont marquees par l’association d’une myosite inflammatoire et de signes caracteristiques de connectivites signant le chevauchement. Conclusion Les myosites de chevauchement a debut pediatrique forment un groupe d’affections heterogenes et distinctes des formes classiquement decrites chez l’adulte.