Secondary hemophagocytic lymphohistiocytosis following bacterial pneumonia managed with dexamethasone monotherapy: a case report

Introduction: Secondary hemophagocytic lymphohistiocytosis (HLH) is a rare hyperinflammatory syndrome in adults, resulting from uncontrolled immune activation and a cytokine storm, and is frequently misdiagnosed because its manifestations closely resemble severe infection or sepsis, particularly when triggered by bacterial pneumonia. Case presentation: A 63-year-old woman presented with 1 week of fever, cough, and dyspnea despite outpatient antibiotic treatment. Investigations confirmed right-sided lobar pneumonia caused by Streptococcus pneumoniae . Despite targeted intravenous antibiotics, she developed worsening cytopenias, hyperferritinemia, hypertriglyceridemia, and splenomegaly. Bone marrow aspiration revealed hemophagocytosis, confirming the diagnosis by fulfilling five out of the eight HLH-2004 criteria and an HScore of 200. Due to her age and treatment preferences, the patient was started on dexamethasone monotherapy. She showed rapid clinical and laboratory improvement within three days and remained stable during follow-up. Clinical discussion: Infection-associated HLH is commonly triggered by viral infections but can rarely occur secondary to bacterial infections, such as S. pneumoniae . HLH should be suspected when symptoms worsen despite appropriate antimicrobial therapy. Early recognition using the HLH-2004 criteria and HScore is vital for improving patient outcomes. Immunosuppressive therapy is essential to interrupt immune system activation and prevent organ failure. Although standard regimens include etoposide-based treatments, decisions must consider patient age, comorbidities, and tolerance. Conclusion: This case highlights the need for increased suspicion of HLH in patients with unremitting fever and progressive cytopenias, despite appropriate antimicrobial therapy. Dexamethasone monotherapy may be considered a potential alternative for select patients who cannot tolerate or do not consent to cytotoxic chemotherapy.