Macrophage activation syndrome (MAS) constitutes one subtype of the hyperinflammatory syndrome hemophagocytic lymphohistiocytosis (HLH), and the term MAS-HLH was recently proposed for HLH with underlying autoimmune/autoinflammatory conditions. The mortality of MAS-HLH has been estimated to 5-10%. Here we report our experiences with moderately dosed etoposide in severe MAS-HLH, administered with the objective to effectively reduce severe hyperinflammatory activity with limited side effects.In addition to conventional anti-inflammatory treatment, moderately dosed etoposide was administered to seven children affected by rapidly progressing MAS-HLH with central nervous system (n=5) and/or pulmonary (n=5) involvement. Three had underlying systemic onset juvenile idiopathic arthritis (sJIA), two atypical sJIA (no arthritis at diagnosis), and two systemic lupus erythematosus. We performed lymphocyte cytotoxicity analyses in all seven and genetic analyses in six.All children promptly responded to moderately dosed etoposide (50-100 mg/m2 once weekly), added to conventional MAS-HLH treatment which was considered insufficient. The mean accumulated etoposide dose was 671 mg/m2 (range 300-1,050 mg/m2), as compared to 1,500 mg/m2 recommended the first 8 weeks of the HLH-94/HLH-2004 protocols. One child developed neutropenic fever and another neutropenic sepsis (neutrophils 0.3x109/L at therapy onset). Five/seven children had low percentages (<5%) circulating NK-cells prior to or in association with diagnosis; NK-cell activity was pathologically low in two/five children studied. Disease-causing variants in HLH-associated genes were not found. All children were alive at latest follow-up (2-9 years after onset); neurological symptoms had normalized in four/five affected children.Moderately dosed etoposide may be beneficial in severe and/or refractory MAS-HLH.
AnnaCarin Horne, Tatiana von Bahr Greenwood, Samuel C C Chiang, Marie Meeths, Caroline Björklund, Maria Ekelund, Peter Erensjö, Stefan Berg, Stefan Hagelberg, Yenan T Bryceson, Ulf Andersson, Jan-Inge Henter