When Skin-Limited Langerhans Cell Histiocytosis Becomes Life-Threatening: Severe Treatment-Related Morbidity in a Prematurely Born Infant-Case Report.

Background and Clinical Significance: Skin-limited Langerhans cell histiocytosis (LCH) is a clinically heterogeneous disease, ranging from self-healing forms to fulminant multi-organ failure, the latter being more often described in infants, especially preterm neonates. The optimal therapy for cutaneous LCH remains controversial; the possibilities vary from a watchful waiting approach to systemic chemotherapy. Case Presentation: This case report describes an exceptionally rare and clinically challenging course of skin-limited LCH in a prematurely born infant treated at the Department of Oncology and Hematology, Children's Hospital Zagreb, Croatia. At presentation, the patient exhibited several features suggestive of aggressive disease biology. However, therapeutic decision-making was complicated by extreme prematurity and young age, both of which significantly increased vulnerability to treatment-related toxicity. Following failure of topical therapy, systemic treatment was initiated according to the LCH-IV trial, primarily due to concerns regarding potential evolution into multisystem LCH. During treatment, the patient developed multiple life-threatening complications, namely severe infections (Staphylococcus aureus endocarditis, Pneumocystis jirovecii pneumonia, and Enterobacter cloacae sepsis), aggravated by secondary hypogammaglobulinemia, neutropenia, and iatrogenic adrenal insufficiency. Conclusions: The varied nature of cutaneous LCH underscores the necessity for a tailored treatment approach. When deciding on the treatment modality, clinicians should weigh the benefits of aggressive therapies, ensuring better disease control, against the potential for severe adverse effects, particularly in young, fragile infants with immature immunity.