- Background Hemophagocytic lymphohistiocytosis (HLH) is caused by an excessive activation of nonmalignant macrophages. Renal lesions have been described in association with, but always after, HLH diagnosis. Case-diagnosis We describe a previously healthy 26- month-old girl who presented originally with steroid-responsive nephrotic syndrome (NS), but after 4 months, on the first NS relapse, experienced numerous complications (many of them reported to accompany NS as single events). Clinical and laboratory signs of HLH evolved with time and led to deterioration of her condition and death, within 5 months of her original presentation. Conclusions To our knowledge, this is the first report of NS antedating the presentation of HLH.