RESUMEN
Acquired haemophagocytic lymphohistiocytosis (HLH) is a condition involving cytokine overproduction by defective cytotoxic T lymphocytes and natural killer cells, resulting in life-threatening cytopenias and multiorgan infiltration and dysfunction. Triggers for acquired HLH vary and include viruses, malignancies and autoimmune conditions. Recent reports suggest that HLH may be underdiagnosed owing to variable clinical presentations, diagnostic criteria and a low level of awareness on the part of medical personnel, thus delaying prompt treatment and contributing to high mortality rates. Five patients in whom acquired HLH was diagnosed, following bone marrow investigations, for the period of May - September 2013 are presented. All were at an advanced stage of their disease at time of diagnosis. The three patients who were HIV-positive had a coexisting malignancy at the time of HLH diagnosis, which may have triggered HLH. A definite trigger was not identified in the remaining two HIV-negative patients despite early concerns regarding autoimmune disease. Two patients received timeous diagnosis, started chemotherapy and are currently improving. The remaining three succumbed to their illness. Adult acquired HLH may be more common in the acute care setting than currently appreciated. As awareness of this condition and its treatment is currently low, it may remain undiagnosed until the disease has evolved into multiorgan failure. Fever in the absence of infectious agents, marked hyperferritinaemia, unexplained cytopenias, organomegaly or liver dysfunction should raise the suspicion of HLH. Timeous introduction of therapy will improve outcomes.