Niemann-pick disease is a severe disorder in sphingolipid metabolism and esterification of cholesterol which results in accumulations of sphingomyelin in different tissues. This disease is characterized with hepatosplenomegaly, fever and foam cell appearance in microscopic examination of bone marrow, liver and spleen. The case presented in this study is a four-month-old female infant with chief complaint of fever, pancytopenia, and severe abdominal distension, and anemia since 10 days before admission to our hospital. The case was the third child of the family born with cesarian section and without any significant health problems before hospitalization. Her siblings had both died in the hospital, but the cause of death is unknown. Significant laboratory findings include WBC=1500 (neutrophil 70%), RBC=2,000,000, Hb=5.5 g/dl, Plt= 30,000, CRP=3+, ESR=45, ALT=300 IU, and AST-150 IU. No other abnormal findings were observed in laboratory report. Thoracoabdominal X-ray revealed significant hepatosplenomegaly. Her parents were cousins. Soon after admission to our hospital, she received a wide spectrum antibiotic, but underwent ventilator due to sepsis. Unfortunately,  our therapeutic management was not successful, and the patient died due to septicemia the next morning. After obtaining written consent of the parents, the patient underwent necropsy, which revealed lipid storage disease, Niemann-pick disease. The purpose of our study was to emphasize the importance of necropsy and follow-up until a definite diagnosis.