[One complication can mask another: chance discovery of a rare lesion during screening for arthritis of the hip].

The authors report the case of a new born baby in whom at the fourth day of life, a severe hypocalcemia was discovered. An umbilical arterial catheterization was performed. The evolution was characterized by a staphylococcic septicemia with hip arthritis and partial immune deficit. The mid term survey of the joint status, allowed the unexpected discovery, during an examination held under general anesthesia, of a probable mycotic aneurysm, by abdominal palpation. The lesion was localized on the right common iliac artery and was successfully treated by resection; arterial continuity was possible without venous patch nor prosthesis.