Hemophagocytic lymphohistiocytosis

This code identifies a rare and severe immune dysregulation syndrome characterized by uncontrolled activation and proliferation of histiocytes and lymphocytes, leading to widespread inflammation and organ damage. It involves excessive cytokine production and can be primary (genetic) or secondary (acquired due to infection, malignancy, or autoimmune disease).

Assign this code for patients diagnosed with hemophagocytic lymphohistiocytosis (HLH), confirmed by clinical criteria such as fever, splenomegaly, cytopenias, hypertriglyceridemia, hypofibrinogenemia, elevated ferritin, elevated soluble CD25, and absent or low NK cell activity, along with hemophagocytosis in bone marrow, spleen, or lymph nodes. Documentation should clearly state the diagnosis of HLH.

• Distinguish between primary (familial) and secondary HLH; while this code covers both, further specificity may be needed for research or registry purposes.
• Code any underlying conditions (e.g., infections, malignancies, autoimmune diseases) that trigger secondary HLH as additional diagnoses.
• Ensure documentation supports the diagnostic criteria for HLH, as it can be confused with severe sepsis or other inflammatory conditions.