A Challenging Diagnosis of Hemophagocytic Lymphohistiocytosis with Unusual Pulmonary Manifestations: A Case Report.

Introduction: Hemophagocytic Lymphohistiocytosis (HLH) is a rare, aggressive, and life-threatening disorder characterized by sustained but ineffective immune system activation that leads to severe and systemic hyperinflammation. It may occur as a genetic or sporadic condition, often triggered by an infection. The multifaceted pathogenesis results in a wide range of non-specific symptoms, signs, and laboratory findings that challenge its recognition. The pulmonary involvement is underdiagnosed and may manifest as pneumonia, which can lead to respiratory failure. Despite the great improvement achieved in terms of survival, a considerable proportion of patients with HLH still die from progressive disease. Case Presentation: We discuss the case of a unique form of respiratory distress and multiorgan failure with inconclusive radiological and lung biopsy investigations. The patient was finally diagnosed, by genetic analysis, with HLH, and promptly treated as per HLH-94 treatment protocol. Conclusion: This case report aims to emphasize that clinical, laboratory, instrumental, and even pathological findings in HLH might not be unequivocal; nonetheless, a rapid diagnosis and treatment are mandatory, given the high mortality of the disease.