A hidden enemy: Understanding the hemophagocytic syndrome in children under five years of age in a high-complexity institution in southwestern Colombia.

Introduction. Hemophagocytic syndrome is an under-recognized condition with high mortality in the pediatric population. It is characterized by excessive activation of immune cells and cytokine release, leading to persistent inflammation. Hemophagocytic syndrome can be primary or secondary and associated with different triggers. Objective. To describe 12 clinical cases of children under five years of age with hemophagocytic syndrome in a high-complexity institution in southwestern Colombia. Materials and methods. We present a retrospective series of 12 cases of hemophagocytic syndrome in children under five years of age treated at a high-complexity institution in Colombia between 2019 and 2022. Results. The median age of the patients was one year and 7 were male. Fever and splenomegaly were the most common clinical manifestations observed in 11 of the patients. The predominant laboratory findings included hyperferritinemia (n = 11), hypertriglyceridemia (n = 10), bicytopenia (n = 6), and pancytopenia (n = 2). Eleven cases had elevated lactate dehydrogenase levels. Genetic studies were conducted in 7 patients. Regarding treatment, the full HLH-2004 protocol was administered to 5 cases, while 3 underwent hematopoietic stem cell transplantation. Three patients died. Conclusion. We highlight the complexity of the hemophagocytic syndrome, especially in children under five years old, because the low prevalence and non-specific clinical presentation of the disease contribute to its underdiagnosis. Emphasis is placed on identifying triggers, performing genetic evaluation for accurate and early diagnosis, adopting a multidisciplinary approach, and considering early hematopoietic stem cell transplantation to improve morbidity and mortality outcomes.