1. Internal Medicine. Temple University Hospital, Philadelphia, PA, USA
2. Systemic Autoimmune Diseases Unit. HGR #36, IMSS, Puebla, Mexico
3. Research Department. Unidad de Alta Especialidad, Hospital de Especialidades CMN La Raza, Mexico DF, Mexico
4. Department of Autoimmune Diseases. Institut clinic de Medicina i Dermatologia, Hospital Clinic, Barcelona, Spain