Hemophagocytic Lymphohistiocytosis (HLH): Review of Bone Marrow Morphology and Correlation with Laboratory Findings
Clinical and laboratory data were collected and correlated with morphologic findings.
Results: HLH pts and CG aged 0.2 to 27 yrs (average=6.9 yrs). Average BM cellularity was 76% in HLH pts compared to 68% in CG (no significant difference). HA was present in 88% of HLH pts. A significant increase in histiocytes and atypical lymphocytes was seen in a significantly higher proportion of HLH pts compared to CG (p<0.05). HLH pts showed a significantly higher grade of HA compared to CG (p<0.05). The engulfed hematopoietic cells were intact in HLH. In contrast, they were degenerated and accompanied by cellular debris and hemosiderin pigment in HLH mimics. The grade of HA in HLH BMs did not correlate with cytopenias, Ferritin or Triglyceride levels, natural killer or cytotoxic T cell function, Perforin expression, CD4/CD8 ratio, or soluble IL-2 receptor levels.
Conclusions: BM examination is critical for HLH diagnosis and has a sensitivity of 88%. Unlike previous reports of BM hypocellularity in HLH, our study showed an average BM cellularity of 76%. An HA grade-2, increased histiocytes and atypical lymphocytes, and presence of intact engulfed hematopoietic cells are key morphologic features of HLH. In contrast, HLH mimics often show absent or rare HA, no significant increase of histiocytes and atypical lymphocytes, and degenerated engulfed cells accompanied by cellular debris and hemosiderin pigment. The grade of HA in HLH does not correlate with laboratory findings.
Monday, March 9, 2009 11:15 AM
Platform Session: Section H2, Monday Morning