Xanthogranulomatous pyelonephritis in children, contrary to adult onset, rarely is associated with non-function or calcification. The lesion is predominantly on the left side in children. There appears to be a normal humoral but temporarily impaired cellular immune response in addition to sustained depression of polymorphonuclear chemotaxis. The etiology of this is uncertain but may be attributed partially to hyperosmolarity of serum and urine, and to leukocyte specific antinuclear antibodies. The presence of leukocyte specific antinuclear antibody or cold agglutining may interfere with normal phagocyte chemotaxis requiring tissue macrophages to produce a xanthogranulomatous reaction to bacterial invasion.