Haemophagocytic lymphohistiocytosis in association with granular lymphocyte proliferative disorders in early childhood: characteristic bone marrow morphology

Five paediatric cases of haemophagocytic lymphohistiocytosis (HLH) which showed proliferation of granular atypical lymphocytoid cells in bone marrow are reported. All cases were girls aged 8 months to 4 years who had marked hepatosplenomegaly. Marker analysis on peripheral blood mononuclear cells revealed an increase in the CD3⁺HLADR⁺ subset in three cases and the CD^3?CD56⁺ subset in one case. An Epstein-Barr virus genome was detected in three cases, and monoclonality was confirmed in two cases. A characteristic morphology of large granular lymphocytes (LGL) was identified, with elongated bizarre features that resembled horsetail-, tadpole-, cucumber- or shooting star-type configurations on the bone marrow smear. Serum concentrations of soluble interleukin-2 receptor and interferon-gamma were elevated in all cases. All five cases required multi-agent chemotherapy which resulted in two complete remissions, two partial remissions and one no response. Refinement of treatment is required for these paediatric GLPD cases which probably comprise a specific high-risk subgroup among secondary HLH patients which had previously escaped notice.