DISEASE CHARACTERISTICS:

• Newly diagnosed hemophagocytic lymphohistiocytosis (HLH) meeting 1 of the following criteria*:

  • Diagnosis by molecular/genetic methods

  • Diagnosis by meeting 5 out of 8 of the following criteria:

    • Clinical criteria:

      • Fever
      • Splenomegaly

    • Laboratory criteria:

      • Cytopenias affecting ≥ 2 of 3 lineages in the peripheral blood, including the following:

        • Hemoglobin < 9.0 g/dL (< 10.0 g/dL in infants < 4 weeks of age)
        • Platelet count < 100,000/mm^3
        • Neutrophil count < 1,000/mm^3

      • Hypertriglyceridemia and/or hypofibrinogenemia:

        • Fasting triglycerides ≥ 3.0 mmol/L (i.e., ≥ 265 mg/dL)
        • Fibrinogen ≤ 1.5 g/L

    • Histopathologic criteria:

      • Hemophagocytosis in bone marrow, spleen, or lymph nodes

        • No evidence of malignancy

    • New diagnostic criteria:

      • Low or absent natural killer (NK) cell activity
      • Ferritin ≥ 500 mcg/L
      • Soluble CD25 (i.e., soluble interleukin-2 receptor) ≥ 2,400 U/mL NOTE: *Patients who do not meet the diagnostic criteria for HLH but who have a strong clinical suspicion of HLH may be eligible at the discretion of the investigator
• Primary HLH (i.e., familial hemophagocytic lymphohistiocytosis [FLH]) OR secondary HLH (i.e., severe acquired form of HLH)

• Acceptable donor meeting 1 of the following criteria:

  • HLA-identical related donor
  • Matched unrelated donor
  • Mismatched unrelated donor
  • Familial haploidentical donor

PATIENT CHARACTERISTICS:

• Not specified

PRIOR CONCURRENT THERAPY:

• No prior cytotoxic treatment for HLH
• No prior cyclosporine treatment for HLH