Abstract Introduction Langerhans cell histiocytosis (LCH) is a rare proliferative disorder of myeloid dendritic cells that can involve bone, lung, or skin. In children, respiratory manifestations such as wheezing or cough may mimic asthma, delaying diagnosis. This case highlights an uncommon presentation of unifocal LCH initially mistaken for asthma in a previously healthy child. Case Presentation A 4-year-old boy from Ecuador, previously healthy, presented to the emergency department with two hours of progressive dyspnea, dry cough, and diffuse wheezing. His parents reported two prior mild episodes of nocturnal cough over the preceding month, attributed to cold exposure. He had no history of asthma, allergy, or chronic respiratory illness. On examination, SpO2 was 95% on room air, respiratory rate 28/min, and mild intercostal retractions were noted. Bilateral wheezing was audible on auscultation. A presumptive diagnosis of acute asthma exacerbation was made, and inhaled salbutamol plus budesonide were administered, producing marked improvement after one hour. During routine examination, a persistent tender swelling over the right frontal region was observed. The mother reported it had persisted for a month after minor trauma. Skull X-ray revealed a lytic defect in the right frontal bone, confirmed by cranial CT and 3D reconstruction showing a 4 cm osteolytic lesion with irregular borders and subgaleal hematoma (Figure 1A-B). Routine laboratory tests were normal. Surgical excision of the lesion revealed large polygonal histiocytes with grooved nuclei and numerous eosinophils, consistent with eosinophilic granuloma. Immunohistochemistry was positive for CD1a, S100, cyclin D1, and CD68, confirming Langerhans cell histiocytosis (Figure 1C). The patient received induction chemotherapy with vinblastine (4.5 mg IV weekly for 12 weeks) and prednisone (10 mg PO q8h for 20 days with taper). Bone marrow biopsy showed normal cellularity, excluding systemic involvement. Chest imaging revealed no pulmonary lesions. Transient leukopenia (WBC 2,800/µL) prompted brief treatment suspension; therapy was resumed and completed successfully. Follow-up labs normalized, and the patient remains in remission under oncology follow-up. Discussion This case underscores a diagnostic pitfall where acute wheezing led to a presumptive diagnosis of asthma, masking underlying unifocal LCH. Although pulmonary involvement was absent, respiratory symptoms may reflect cytokine-mediated airway inflammation. Recognition of atypical findings—such as persistent bone lesions in children with new-onset wheezing—should prompt imaging. Histopathological confirmation with CD1a and S100 positivity remains diagnostic. Early vinblastine-based therapy achieves excellent outcomes. Multidisciplinary coordination ensures accurate diagnosis and durable remission. This abstract is funded by: NO FUNDING
Briones-Zamora et al. (Fri,) studied this question.