1. Department of Pediatric Rheumatology, University Children’s Hospital “Ivan Mitev”, Medical University of Sofia, Sofia, Bulgaria
2. Department of Pediatric Diseases, Alexandrovska Hospital, Medical University of Sofia, Sofia, Bulgaria
3. Department of Clinical Immunology with Stem Cell Bank, Alexandrovska Hospital, Medical University of Sofia, Sofia, Bulgaria
4. Imaging Studies Department, Saint Ekaterina University Multiprofile Hospital for Active Treatment, Medical University of Sofia, Sofia, Bulgaria
5. Pediatric Department, Saint Marina Hospital, Medical University of Varna, Varna, Bulgaria