From diagnosis to treatment: a successful case of haemophagocytic lymphohistiocytosis of presumed bacterial aetiology in an adult.

Haemophagocytic lymphohistiocytosis (HLH) affects patients across all age groups and can be classified as either primary HLH (P-HLH) or secondary HLH (S-HLH). The latter is associated with clinical conditions that disrupt normal immunological responses, such as infections, neoplasms or autoimmune diseases. Although HLH can occur sporadically in healthy individuals, it is more frequently observed in patients with haematological malignancies and autoimmune disorders. The diagnostic process for HLH is often challenging due to its non-specific signs and the absence of pathognomonic findings. The primary objective in treating S-HLH is to eliminate the underlying trigger and control immunological hyperactivation, making the identification and treatment of triggers critically important. Prompt diagnosis and treatment are essential, as the mortality rate remains high. In this context, we present the case of a young woman diagnosed with idiopathic S-HLH, likely triggered by a bacterial infection. The diagnosis was achieved due to a high index of clinical suspicion for S-HLH. The patient exhibited an excellent response to antimicrobial therapy, resulting in the complete resolution of haemophagocytosis. The authors deem it important to present this case to enhance awareness of S-HLH diagnosis, as well as the investigation and management of potential triggers.