# Trends in Mortality Rates From Hemophagocytic Lymphohistiocytosis in the United States From 2010 to 2023

## TL;DR

Mortality rates from a rare and deadly immune disorder called hemophagocytic lymphohistiocytosis have risen sharply in the U.S. from 2010 to 2023.

## Contribution

This study is the first to document a consistent and significant 12-fold increase in age-adjusted mortality rates for HLH in the U.S. over a 13-year period.

## Key findings

- Age-adjusted mortality rates from HLH increased 12-fold from 2010 to 2023.
- The mortality trend was consistent across all U.S. census regions and most demographic groups.
- Yearly increases in mortality were statistically significant for most years in the study period.

## Abstract

Hemophagocytic lymphohistiocytosis (HLH) is a severe, life-threatening condition marked by uncontrolled T-lymphocyte and macrophage-mediated inflammation, usually secondary to an underlying malignancy or infection in adults. It leads to multiorgan failure and death if not promptly recognized and treated; adult secondary HLH carries an overall mortality rate of 57% in an ICU population regardless of treatment. We examined trends in age-adjusted mortality rates from the Centers for Disease Control and Prevention's Wide-ranging Online Data for Epidemiologic Research (CDC WONDER) database to further characterize this interesting multinational finding in an otherwise rare disease. Age-adjusted mortality rates (AAMRs) from HLH showed consistent yearly increases, most of which were statistically significant, with an overall 12-fold rise from 2010 to 2023. This trend was mirrored in all census regions and in most demographic categories.