Diagnosis of HLH; diagnostic criteria and laboratory results of cases
| (A) The diagnosis of HLH can be established if criterion 1 or 2 is fulfilled | |||
| A molecular diagnosis consistent with HLH | |||
| Diagnostic criteria for HLH fulfilled (5 of 8 criteria below) | |||
| Fever | |||
| Splenomegaly | |||
| Cytopaenias (affecting >2 of 3 lineages in peripheral blood) Haemoglobin <9.0 g/dL, platelets <100×109/L, neutrophils <100×109/L | |||
| Hypertriglyceridaemia and/or hypofibrinogenaemia Fasting triglycerides ≥3.0 mmol/L, fibrinogen <1.5 g/L | |||
| Haemophagocytosis in bone marrow or spleen or lymph nodes. No evidence of malignancy | |||
| Low or no natural killer (NK) cell activity | |||
| Ferritin ≥500 µg/L | |||
| sCD25 (soluble interleukin (IL)-2 receptor) ≥2400 U/mL | |||
| (B) Clinical and laboratory features | Case 1 | Case 2 | Case 3 |
| Time to onset symptoms post vaccination (days) | 5 | 7 | 8 |
| Temperature (38.4–39.4°C) | 39.3 | 39.2 | 41.2 |
| Organomegaly | Yes (hepatomegaly) | No | Yes (splenomegaly) |
| Haemoglobin (Normal range (NR) 120–150 g/L) | 10.1 | 11.9 | 10.5 |
| Platelets (NR 150–400 x 10×9/L) | 54 | 69 | 319 |
| Ferritin (NR 15–400 µg/L) | 159 076 | 5529 | 58 255 |
| Lactate dehydrogenase (LDH) (NR 90–275 iU/L) | 536 | 1178 | 541 |
| Triglyceride (NR 0.5–2.3 mmol/L) | 6.3 | 2 | 2.7 |
| Fibrinogen (NR 2.12–4.88 g/L) | 0.7 | 0.94 | 4.17 |
| Alanine aminotransferase (ALT) (NR 0–35 iu/L) | 132 | 47 | |
| Troponin (NR <14 ng/L) | 299 | 312 | 42 |
| Haemophagocytosis on bone marrow biopsy | Yes | Yes | Yes* |
| sCD25 (0–2500 pg/mL) | 4833 | 9232 | 3575* |
| HScore for HLH (% probability) | 259 (>99) | 220 (96) | 219 (96) |
(A) HLH-2004 diagnostic. (B) Laboratory results of cases 1–3 at time of diagnosis.
*In case 3, undertaken after 3 days of methylprednisolone.
HLH, haemophagocytic lymphohistiocytosis.