Background/Purpose:

Hemophagocytic syndrome (HPS) is a rare fatal condition of excessive immune activation. Association of hemophagocytosis with certain rheumatologic diseases is called macrophage activation syndrome (MAS). We studied the trend of hemophagocytic syndrome and association of rheumatologic conditions over nine years in a large US inpatient database called the Nationwide Inpatient Sample (NIS).

Methods:

NIS (2006 – 2014) was used to identify adult hospitalizations ≥18 year of age with a listed discharge diagnoses of hemophagocytic syndrome based on ICD-9 diagnosis code 288.4. The code includes multiple white blood cell disorders, including the MAS. Age-and-sex-standardized rates (per 1 million hospitalizations), mortality, mean cost and length of stay (LOS) were calculated for the respective years. Joinpoint regression analysis was used to analyze the yearly trends.

Results:

A total of 5679 discharges with the diagnoses of hemophagocytic syndrome were identified among 288.15 million (288,156,693) discharges over nine years (2006-2014).

Hemophagocytic syndrome was more commonly seen in males (57%) vs females (43%) and younger (mean age 45.5 vs 57.1 years). Higher predominance was noted in urban, large and teaching hospital settings. More patients HPS were admitted on emergent basis rather than elective. The trend of hospital discharges for hemophagocytic syndrome was significantly increasing over the years (1.43 per million in 2006 to 44.7 per million in 2014), likely due to increased identification of the entity. Association with rheumatologic conditions as primary diagnoses category was recorded in 3.75% of the total cases of hemophagocytic syndrome. The cost of hospitalization with HPS was $51,979 vs $12,340 in those without HPS. Mean LOS remained significantly higher (14.8 days vs 5 days). The mortality and mean cost and LOS with HPS was significantly higher than those without HPS throughout all years (Table 1).

Conclusion:

The increasing trend of prevalence and more so in the urban settings may be associated with increasing identification of the condition in inpatient setting. Increased awareness of this rare and fatal condition may help in early identification with an opportunity to better treat with available resources as well as to conduct further studies. The association with specific rheumatologic conditions needs further studies.