Haemophagocytic Lymphohistiocytosis
Pronunciation: hee-moh-FAJ-ih-SIT-ik lim-foh-his-tee-oh-sy-TOH-sis
Also written as: HLH — Haemophagocytic Lymphohistiocytosis
A life-threatening hyperinflammatory syndrome caused by uncontrolled activation and proliferation of cytotoxic T lymphocytes and macrophages, resulting in widespread tissue destruction and cytopenias.
Full Definition
Haemophagocytic lymphohistiocytosis (HLH) is a severe, potentially fatal syndrome of immune dysregulation in which activated macrophages engulf erythrocytes, leucocytes, platelets, and their precursors—a process termed haemophagocytosis or erythrophagocytosis. It occurs in primary (familial, genetic) and secondary (reactive, infection-triggered) forms, with Epstein–Barr virus being a common trigger in children. Diagnostic criteria include fever, splenomegaly, cytopenias, hypertriglyceridaemia, hypofibrinogenaemia, haemophagocytosis on bone marrow biopsy, low or absent NK-cell activity, elevated ferritin, and elevated soluble CD25. In pathology reports, the finding of haemophagocytosis in bone marrow or lymph node biopsies must be described precisely. Editors should note both the British spelling 'haemophagocytic' and the American spelling 'hemophagocytic,' and apply the house style consistently throughout a document.
Usage
Usage note: Standardize spelling (haemophagocytic vs hemophagocytic) to house style; ensure HLH is expanded on first use. 'Macrophage activation syndrome' is the preferred term in rheumatological contexts but describes an overlapping entity.
In Context
- "Bone marrow trephine biopsy demonstrated florid haemophagocytosis consistent with haemophagocytic lymphohistiocytosis in the context of EBV viraemia." — Pediatric haematopathology report
- "The manuscript consistently alternated between 'haemophagocytic' and 'hemophagocytic'; the copy editor should standardize to the journal's preferred British spelling throughout." — Copy-editing annotation