Acknowledgments The authors thank Dr. Brenda Quintana, Section of Immunofluorescence, Service of Hemotherapy and Immunohematology, Hospital de Agudos "J. M. Ramos Mejía", Gobierno de la Ciudad de Buenos Aires, for her worthy help in providing microscopic patterns. We also thank the laboratory Biocientífica S.A. for sponsoring and editing this scientific material. Immunofluorescence patterns have been produced by Inmunofluor® kits. Immunoperoxidase patterns have been produced by Peroxiset® kits. Inmunofluor® and Peroxiset® are registered trademarks of Biocientífica S.A., Buenos Aires, Argentina. Any and all part of this text shall not be reproduced in any format whatsoever without the editor's written authorization.