Table 1.

Main Clinical, Histopathological, and Laboratory Features^a,b

Feature	N	Patients	%
Epidemiology
Age at diagnosis (y), mean ± SD	150	51.4±21.5
Sex: male	151	91	60.3
Born outside Spain	151	26	17.2
Underlying diseasesc
Autoimmune/rheumatologic diseases	151	53	35.1
Systemic lupus erythematosus	151	13	8.6
Inflammatory bowel disease	151	7	4.6
Still disease	151	7	4.6
Rheumatoid arthritis	151	6	4.0
Inflammatory myopathies	151	4	2.6
Mixed connective tissue disease	151	4	2.6
Vasculitis	151	3	2.0
Other autoimmune diseases	151	9	6.0
Neoplasia	151	48	31.8
T/NK-cell lymphoma	151	14	9.3
B-cell lymphoma	151	12	7.9
Other hematological neoplasia	151	11	7.3
Solid neoplasia	151	11	7.3
Chronic viral infections	151	32	21.2
Transplantation	151	8	5.3
No underlying disease identified	151	42	27.8
Active immunosuppressive treatment	151	42	27.8
Clinical presentation
a. Symptoms/organs involved
Duration of symptoms (wk), mean ± SD	151	3.7±4.5
Fever (>37.5°C)	151	140	92.7
Splenomegaly	151	96	63.6
General symptoms	151	71	47.0
Hepatomegaly	151	76	50.3
Peripheral adenopathies	151	74	49.0
Pulmonary involvement	151	70	46.4
Renal involvement	151	51	33.8
Gastrointestinal involvement	151	46	30.5
Skin lesions	151	42	27.8
CNS involvement	151	35	23.2
Arthralgias/myalgias	151	29	19.2
b. Hematological & coagulation
Anemia
Hemoglobin <12 g/dL	149	140	94.0
Hemoglobin <9 g/dL	149	104	69.8
Hemoglobin <7 g/dL	149	34	22.8
Thrombocytopenia
Platelets <150,000 cells per mm3	150	136	90.7
Platelets <100,000 cells per mm3	150	128	85.3
Platelets <10,000 cells per mm3	150	21	14.0
Leukopenia (leukocytes <4000 cells per mm3)	150	115	76.7
Neutropenia
Neutrophils <1500 cells per mm3	148	89	60.1
Neutrophils <1000 cells per mm3	148	69	46.6
Neutrophils <500 cells per mm3	148	34	23.0
Hypofibrinogenemia (fibrinogen <1.5 g/L)	146	30	20.5
Disseminated intravascular coagulation	151	20	13.2
c. Biochemical
Hyperferritinemia
Ferritin >500 ng/mL	140	135	96.4
Ferritin >1000 ng/mL	140	127	90.7
Ferritin >10,000 ng/mL	140	48	34.3
Hypertriglyceridemia
Triglycerides >150 mg/dL	140	128	91.4
Triglycerides >265 mg/dL	140	93	66.4
Hyponatremia
<135 mmol/L	148	92	62.2
<130 mmol/L	148	42	28.4
Raised ALT transaminase
ALT transaminase >40 IU/L	148	114	77.0
ALT transaminase >100 IU/L	148	78	52.7
Raised AST transaminase
AST transaminase >40 IU/L	147	117	79.6
AST transaminase >100 IU/L	147	84	57.1
Raised lactate dehydrogenase
Lactate dehydrogenase >500 IU/L	146	115	78.8
Lactate dehydrogenase >1000 IU/L	146	74	50.7
d. Hemophagocytosis
Histopathological confirmation	148	138	93.2
e. HScore,d median (IQR)	126	230 (200-267)

^aALT = alanine aminotransferase; AST = aspartate aminotransferas; CNS = central nervous system; IQR = interquartile range; NK = natural killer.

^bUnless otherwise specified, the values are number (%).

^cPatients may have more than 1 underlying disease.

^dOnly calculated in patients with all ítems measured/carried out (n=126).