An eleven-year old girl's case of an inflammatory process of the right lower abdomen is described, with a positive agglutination reaction to "Y. pseudotuberculosis", serotype I-A. The surgical operation disclosed a normal coecal appendix as well as a mass of clustered ganglionar adenopathies, exclusively located in the ileo-coecal junction. Histologic findings were a pulpar and follicular hyperplasia with mastocytes accumulation and metachromatic staining of capsule and connective tissue. From homogenized ganglionar mass an agent was isolated, further identified as "Y. pseudotuberculosis" type I-A. A comment follows on the frequency of mesenteric lymphadenitis as cause of inflammatory processes of the lower right abdomen in children and the rarity of isolation of "Y. pseudotuberculosis" as etiological agent as compared with the more common "Y. enterocolitica".