Unusual Association of Hemophagocytic Lymphohistiocytosis in Systemic Lupus Erythematosus: Cases Reported at Tertiary Care Center

BACKGROUND Hemophagocytic lymphohistiocytosis (HLH) in the background of systemic lupus erythematosus (SLE) is rare. Inability to discriminate between these two entities may be fatal for the patient. Here we report two cases of SLE with secondary HLH, one of which manifested HLH as the initial presentation, and the significance of HLH's timely diagnosis. CASE REPORT We describe two cases of SLE secondarily affected by HLH, which were diagnosed by various laboratory parameters and detection of profoundly reduced NK cell activity by using flow cytometry. Both our cases on investigation showed hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, and marked reduction or complete absence of NK cell activity. CONCLUSIONS Association of secondary HLH with SLE is rare, and when it occurs, differentiating it from lupus flare requires a high degree of suspicion and awareness of this association. Both have overlapping clinical features, but HLH is characterized by hyperferritinemia, hypofibrinogenemia, hypertriglyceridemia, and a decrease in erythrocyte sedimentation rate (ESR) and NK cell activity unlike SLE. Therefore, early diagnosis of HLH in the background of SLE facilitates timely selection of an appropriate treatment modality to prevent fatal complications.